* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Forces: notes
Relativistic quantum mechanics wikipedia , lookup
Theoretical and experimental justification for the Schrödinger equation wikipedia , lookup
Faster-than-light wikipedia , lookup
Specific impulse wikipedia , lookup
Center of mass wikipedia , lookup
Jerk (physics) wikipedia , lookup
Coriolis force wikipedia , lookup
Velocity-addition formula wikipedia , lookup
Modified Newtonian dynamics wikipedia , lookup
Seismometer wikipedia , lookup
Newton's theorem of revolving orbits wikipedia , lookup
Fictitious force wikipedia , lookup
Hunting oscillation wikipedia , lookup
Centrifugal force wikipedia , lookup
Relativistic mechanics wikipedia , lookup
Classical mechanics wikipedia , lookup
Rigid body dynamics wikipedia , lookup
Relativistic angular momentum wikipedia , lookup
Equations of motion wikipedia , lookup
Classical central-force problem wikipedia , lookup
NAME: _______________________________DATE: ___________Per: _____ 1 Billy Nye Movie Worksheet - Motion 1. _______________________________ put things in motion? 2. Forces are either a ________________________ or ______________________. (both words begin with the letter P) 3. When something is at rest, it remains at rest unless acted on by an _______________________ _____________________. When something is moving it keeps moving unless acted on by an ___________________________ _____________________. 4. “Harder to move” is a property of matter called _________________________ 5. Why does the quarter fall into the glass? (one word) Newton’s First Law: 6. Things at rest stay at ________________, things in motion stay in ____________, unless acted on by an outside ______________. Newton’s Second Law: 7. F= ___________ x ________________ Newton’s Third Law: 8. For every action, there is an equal and __________________________ _______________________ 9. In zero gravity, do the Laws of Motion still apply? Explain… 10. Is the fire extinguisher in the room moving? Yes or No? Explain your reasoning: 2 The Nature of Force: reading comprehension: Read the passage below and define the following vocabulary words: Force Net Force Unbalanced Force Balanced Force Inertia Newton’s 1st Law of Motion Mass Kilogram A force is a push or a pull. Forces are described not only by how strong they are, but also by the direction in which they act. When two forces are exerted in the same direction, they add together. When forces are exerted in opposite directions they are subtracted. (The force in one direction is assigned a positive number while the force in the opposite direction is assigned a negative number.) The overall force on an object, called the NET FORCE, is found by adding the forces together. There can be any number of forces exerted on an object. When there is net force acting on an object, the forces are said to be unbalanced. Unbalanced forces can cause an object to start moving, stop moving or change direction. Unbalanced forces acting on an object will change the object’s motion. When you add the forces together there will be a net force greater than 0. Equal forces acting on an object in opposite direction are called balanced forces. Balanced forces acting on an object will not change the object’s motion. When you add equal forces exerted in opposite directions, the net force is zero. 3 In the 1600s, the Italian thinker Galileo Galilei stated that, whether in motion or at rest, every object resists any change to its motion. This resistance is called inertia. Inertia is the tendency of an object to resist any change in its motion. The English mathematician Sir Isaac Newton restated Galileo’s idea in the first of his three laws of motion. Newton’s First Law of Motion states that an object at rest will remain at rest and an object in motion will remain in motion (at a constant velocity) unless acted upon by an unbalanced force. Newton’s first law of motion is also called the law of inertia. Mass is the amount of matter in an object. The standard unit of mass is the kilogram (Kg). The mass of smaller objects is described in terms of grams (1Kg=1,000g). The amount of inertia an object has depends on its mass. The greater the mass of an object, the greater its inertia. Mass, then, can also be defined as a measure of the inertia of an object. -Science Explorer/Physical Science Answer the Questions Below: 1. How do balanced forces affect the motion of an object? 2. How do unbalanced forces affect the motion of an object? 3. What is Newton’s First Law of Motion? Try to put it in your own words, like you were explaining it to a young child. 4. Give an example of Newton’s First Law of Motion? 4 5. Write the characteristic in the box in appropriate area of the Venn Diagram: Change object’s motion Net force = 0 Have direction Do not change object’s motion Push or pull Net force does not = 0 UNBALANCED FORCES BALANCED FORCES 6. Matching: match each term with its definition by writing the letter of the correct definition on the line beside the term. _______ Newton’s 1st Law a. sum of all forces acting on an object _______ Inertia b. the standard unit of mass _______ Force c. push or pull _______ Unbalanced Force d. can change an object’s motion e. amount of matter in an object _______ Balanced Force f. will not change an object’s motion _______ Net Force g. tendency to resist a change in motion _______ Mass _______ Kilogram h. an object at rest or in motion will remain that way until unbalanced forces act upon them 5 Forces: notes I. A Force is a _________________ or ________________ on an object. Forces will often cause an object to move, or change its current motion. a. List examples of using forces in your daily life: b. The Unit of Force is the ________________________(____) Multiple forces can act on an object at once…..those forces can be combined to find the total or NET FORCE. For example even though a car has a force pushing it forward, gravity is still a force keeping the car on the ground, and friction is a force opposing the car’s motion. c. Forces can be: i. _______________________: object will not change its motion; the net force will equal 0. Example: ii. _______________________: object’s motion will change; net force is greater than O. Example: 6 II. Determining net force: a. Forces are _______________________ which means they need to be determined by not only their numeric value (amount of force in Newton’s) but also their ___________________________. b. When 2 Forces Act in the SAME DIRECTION they are _____________. Examples: Look at the object’s below and calculate the NET FORCE & direction: 1. 2. 5N 12N 40N 14N Net Force = Net Force = c. When 2 forces act in OPPOSITE Directions they are _______________. Examples: Look at the object’s below and calculate the NET FORCE & direction: 1. 2. 33N 75N 88 N 25N Net Force = Net Force = 7 1. Practice: For each of diagram, determine the net force and direction acting on the object. Indicate whether the forces are balanced or unbalanced, and it the motion will change. A. 2N B. 4N 2N 4N C. 8N 10 N D. 10 N E. 5N 2N 2N 10 N 2. Below is a diagram of a tug-0-war. Circle the correct word to complete the sentences in the box. a. The forces shown are PUSHING/ PULLING forces. b. The forces shown are acting in the SAME DIRECTION / OPPOSITE DIRECTIONS. c. The forces are EQUAL/ NOT EQUAL. d . The forces are BALANCED/ UNBALANCED.. e. Motion is to the RIGHT/ LEFT. f. What is the net force? 8 Bill Nye – Gravity Video Worksheet. 1. What keeps the Earth going around the Sun? _______________________ 2. Does gravity push or pull? __________________________ 3. Where does gravity pull towards on Earth? A. Up B. Sideways C. Down D. All directions 4. When the apple and the bowling ball are dropped together: _________ a.) they both hit the ground at the same time b.) the apple hit the ground first c.) the bowling ball hit the ground first 6. What happened to the feather and hammer when dropped? __________________________________ ______________________________________________________________________________________ 8. We use a ____________________to measure our weight. (something you have in your bathroom) 9. As gravity pulls down on us the springs in the scale get _______________. A. Pulled Apart B. Bigger C. Squeezed or compressed D. Heavier 10. The more the scale’s springs get pushed together, the more you _____________________. 11. Weight is calculated by multiplying your _________________ by __________________________. 12. All the planets in orbit around the ___________________ are held in place by gravity. 14. Our Earth is going around the Sun at about _____________ kilometers per hour. 15. Jupiter is larger or smaller than the Earth. (circle one) 16. Jupiter has more or less gravity than the Earth. (circle one) 17. The moon is smaller than the earth, so it has __________________ gravity. 18. The pull of gravity makes the Earth and all planets into this shape: __________________________. 19. With gravity things fall at _____________m/sec2 20. Quote from Skateboarding section: “Gravity will always be the ___________________ no matter where you go or how you do it.” “Gravity keeps the Pizza _____________________________”. 21. Gravity pulls us down toward the _____________________________ of the earth. 9 Friction and Gravity: reading comprehension Read the passage below and define the following vocabulary words: Fiction Gravity Newton’s 2nd Law of Motion Free Fall Projectile Air Resistance Terminal Velocity Universal Law of Gravitation The force that one surface exerts on another when they rub against each other is called fricition. It acts in a direction opposite to the direction of the moving object. Friction will eventually cause an object to come to a stop. The strength of the friction force depends upon the types of surfaces involved and how hard the surfaces push together. Rough surfaces produce greater friction than smooth surfaces. Friction also increases if the surfaces push hard against each other. Sliding friction occurs when solid surfaces slide over each other. Rolling friction occurs when an object rolls over a surface. Fluid friction results when an object moves through a liquid or a gas. As with rolling friction, the force needed to overcome fluid friction is usually less than that needed to overcome sliding friction. Gravity is the force that pulls objects toward each other. When the only force acting on a falling object is gravity, the object is in free fall. All objects in free fall accelerate at the same rate regardless of mass - 9.8m/s2 at sea level. 10 An object that is thrown is called a projectile. While a projectile moves horizontally, the force of gravity pulls it toward Earth. So as it falls, a projectile follows a curved path. Objects falling through air experience a type of fluid friction called air resistance. Air resistance is not the same for all objects. The greater the surface area of an object, the greater the air resistance. Air resistance also increases with velocity (speed and direction). So, as the velocity of a falling object increases, air resistance increases until it is equal to the force of gravity. When forces are balanced, the velocity stops increasing. The greatest velocity that can be obtained by an object in free fall is called terminal velocity. Weight is the force of gravity on a person or object at the surface of a planet. Weight is a measure of the force of gravity on an object, and mass is a measure of the amount of matter in that object. Newton’s second law of motion states that the force can be determined by multiplying the mass times the acceleration of the object. This law can be re-written to find weight. Weight = Mass X Acceleration due to gravity (9.8m/s2) The law of universal gravitation states that the force of gravity acts between all objects in the universe. Any two objects in the universe, without exception, attract each other. The strength of gravity depends on the masses of the objects involved. Since each planet or moon has a different mass, gravity is different on each planet or moon. The strength of gravity also depends on the distance between two objects. The farther apart the objects are, the weaker the force. ~ Science Explorer: Physical Science Use the passage above to answer the following questions: 1. What two factors affect the friction force between two surfaces? 2. What is one way you could reduce the friction between two surfaces? 3. If acceleration due to gravity of all objects in free fall is the same, then why do some objects fall through the air at a different rate? 4. How does mass differ from weight? 11 Matching: match each term with its definition by writing the letter of the correct definition on the line beside the term. _____ 5. Friction _____ 6. Rolling friction _____ 7. Sliding friction _____ 8. Fluid friction _____ 9. Free fall _____ 10. Gravity _____ 11. Terminal velocity _____ 12. Air resistance _____ 13. Weight A. the force that accelerates objects toward Earth B. the kind of friction that exists between oil and a door hinge C. the general term for the force that one surface exerts on anther when they rub against each other D. the kind of friction that slows a falling object E. the state that exists when the only force acting on an object is gravity F. the kind of friction that results when you rub sandpaper against wood G. a measure of the force of gravity on an object H. the kind of friction that results when a wheel turns on a surface I. a falling object reaches this when forces of gravity and air resistance are balanced Gravity and Forces Review: 1. What is a force? _______________________________________________ 2. The unit used to measure force is? ___________________________ 3. Forces that act in the same direction are ______________________. 4. Forces that act in opposite direction are _______________________. 5. To be balanced the net force must equal _________________. 6. The strength of friction depends on what 2 factors: 7. Explain why a crumpled up sheet of paper and a regular flat sheet of paper do not reach the ground at the same time when dropped from an identical height? !!!!Prepare for Forces and Gravity Quiz 1, use all the notes/activities on the above pages!!!! 12 DESCRIBING AND MEASURING MOTION: Read the passage below and define the following vocabulary words: Motion Reference Point Meter Rate Speed Velocity Slope Speed/Velocity Equation Units for Speed An object is in motion when its distance from another object is changing. Whether an object is moving or not depends on your point of view. For example, a woman riding on a bus is not moving in relation to the seat she is sitting on, but she is moving in relation to the buildings the bus passes. A reference point is a place or object used for comparison to determine if something is in motion. An object is in motion if it changes position relative to a reference point. You assume that the reference point is stationary, or not moving. Units of measurement are used to describe an object’s motion. The system of measurement used by scientists all over the world is called International System of Units, or in French, Systeme International (SI). The SI system is based on the number 10. The basic SI unit of length is the meter (m). A meter is a little longer than a yard. To measure the length of an object smaller than a meter, scientists use the metric unit called the centimeter (cm). A centimeter is one-hundredth of a meter, so there are 100 centimeters in a meter. Meters and centimeters can be used to describe the distance an object ravels. 13 Rate is the amount of something that occurs or changes in one unit of time. Speed is a type of rate. The speed of an object is the distance the object travels in one unit of time. To calculate the speed of an object, divide the distance the object travels by the amount of time it takes to travel that distance. Speed measurements consist of a unit of distance divided by a unit of time, such as meters per second. Speed = Distance/Time When an object travels at a constant speed, its speed at any moment during its motion is the same as it is at every other moment. Most objects do not move at constant speeds. To find the average speed of an object, divide the total distance traveled by the total time. An object’s speed tells you how fast it is moving, but not the direction of the motion. When you know both the speed and direction of an object’s motion, you know the velocity of the object. Speed in a given direction is called velocity. Velocity is considered a vector because it contains not only a numeric quantity (magnitude) but also a direction. A line graph in which distance is plotted against time can show the motion of an object. A straight line represents motion at a constant speed. The steepness, or slant, of a line on a graph is called its slope. The faster the motion, the steeper the slope will be. A horizontal line represents an object that is not moving at all because the distance is never changing. ~ Science Explorer Physical Science Use the passage above to help you fill in the following blanks….. 1. A __________________ is the amount of something that occurs in a given unit of time. 2. The steepness of the line on a graph is its _______________________. 3. The _____________ of an object is the distance an object travels in a given amount of time. 4. A __________________ _________________ is an object or place used to determine if an object is in motion. 5. An object is in ___________________ when its distance from a reference point is changing. 6. Speed in a given direction is _____________________. 7. ____________________ can be calculated if you know the distance that an object travels in one unit of time. 8. The basic SI unit of length is the ___________________. 14 9. When an object’s motion is not changing, the object is moving at a __________________ ____________________. 10. On a line graph of distance vs. time (speed graph), a horizontal line represents _______________________________. 11. On a line graph of distance vs. time (speed graph), a straight line represents motion at a _________________________________. 12. On a line graph of distance vs. time (speed graph), the slope of the line indicates how ______________ an object is moving. 13. The steeper the slope the ____________________ the speed of the object. 15 Calculating Speed and Velocity: Speed is a measure of how fast an object is moving. Velocity is a measure of how fast an object is traveling in a certain direction. An object can travel at a constant speed that does not change. However, if the direction in which it is traveling does, the velocity has changed. To find the speed or velocity of an object, use these formulas. You may use a calculator and round your answers to the nearest 10th. In a specific direction 1. Find the velocity of a truck that travels 5. Find the speed of a bicyclist who took an 75miles north in 2.5 hours? hour and a half to travel 10km. List: Equation: List: Substitution: Equation: Substitution: Answer with units: Answer with units: 2. Find the velocity of a plane that traveled 6. Find the velocity of a car that took 7.5 3,000miles west in 5 hours? hours to travel 491.25 miles due south. List: Equation: List: Equation: Substitution: Substitution: Answer with units: Answer with units: 3. Find the average speed of a train that 7. Find the velocity of a train that traveled traveled 543km in 6 hours? 420 miles northeast to northwest between List: Equation: Substitution: two cities in 3.5 hours. List: Answer with units: Equation: Substitution: 4. A plane flies due west for 4.5 hours. It Answer with units: travels a total of 5,400km. What is the 8. A cork floats a distance of 8 ¾ miles velocity? after a period of 3 hours and 30minutes. List: Equation: Substitution: Answer with units: What was its average speed downriver? List: Equation: Substitution: Answer with units: 16 Reading Speed Graphs: SPEED GRAPH Distance (meters) TIME (second) - Speed graphs show the Distance versus the Time s=d/t - To calculate the speed you need to divide the distance by the time - If the line is sloped and straight up then the speed is steady or constant (the same, not changing) Steeper slope = faster speed - If the line is horizontal movement has stopped because the distance is not changing - If the line is curved than the object is accelerating (speeding up), or decelerating (slowing) 17 Use the Graph below to answer the questions that follow. Position is distance. 1. From 0-2 seconds is the skateboarder moving at a constant speed? How do you know? 2. What is the approximate speed of the student on skate board at 2m? (show work) LIST: Equation: S=distance/time s= d= t= 3. What is the approximate speed of the student on the skate board at 6 seconds? (show work) LIST: Equation: S=distance/time s= d= t= 4. What is the approximate speed of the student on the skate board at 8 seconds? (show work) LIST: Equation: S=distance/time s= d= t= 5. What is happening to the motion from 2second to 5seconds? 18 Use the graph on the right to answer the questions below: On Saturday, Ashley rode her bicycle to visit Maria. Maria’s house is directly east of Ashley’s. The graph shows how far Ashley was from her house after each minute of her trip. 1. Ashley rode at a constant speed for the first 4 minutes of her trip. a) How does the graph indicate that she rode at a constant speed for the first 4 minutes? b) What was her constant speed for the first 4 minutes? 2. What was her average speed for the entire trip [average speed = total distant/total time]. 3. a. What is the difference between speed and velocity? b. What was her average velocity for the entire trip? 4. Ashley stopped to talk with a friend during her trip. How far was she from her house when she stopped? Explain how you know. 19 NEWTON’S Law’s of Motion - Notes Sir Isaac Newton was an English Mathematician in the late 1600’s that used some of Galileo’s ideas and developed 3 Basic Laws of Motion. Newton’s First Law of Motion: also called ____________________________. I. ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ a. Inertia:_________________________________________________ b. Example: 1. Describe what happens to the passenger in a car when the breaks are slammed? They are seat belted in…so be serious with your answer 2. Explain why this happened using Newton’s 1st Law: c. The amount of ______________________ an object has depends on its __________________. The _________________ mass an object has the ___________________ the force required to ________________ the object’s motion. (MORE RESISTANCE TO CHANGE = GREAT INERTIA) Use your notes to prepare for a Newton’s 1st Law, speed and velocity quiz!!! 20 Acceleration – reading comprehension. Acceleration is the rate at which velocity changes. Recall that velocity has two components; direction and speed. Acceleration involves a change in either of these components. In science, Acceleration refers to increasing speed, decreasing speed, or changing direction. Any time the speed of an object changes, the object experiences acceleration. That change can be an increase or decrease. A decrease in speed is sometimes called deceleration, or negative acceleration. An object that is changing direction is also accelerating, even if it is moving at a constant speed. A car moving around a curve or changing lanes at a constant speed is accelerating because it is changing direction. Many objects continuously change direction without changing speed. The simplest example of this type of motion is circular, or motion along a circular path. The moon accelerates because it is continuously changing direction as it revolves around earth. Acceleration describes the rate at which velocity changes. To determine the acceleration of an object, you must calculate the change in velocity during each unit of time. This is summarized by the following formula. Acceleration = Final Velocity (Vf) – Initial Velocity (Vi) Time If velocity is measured in meters/second and time is measured in seconds, the unit of acceleration is meters per second per second, which is written as m/s2. If an object is accelerating by the same amount during each unit of time, the acceleration at every point in its motion is the same. If the acceleration varies, however, only the average acceleration can be calculated. For an object moving without changing direction, the acceleration is the change in its speed during one unit of time. A line graph can be used to analyze acceleration by showing speed versus time. When a graph shows speed versus time as a slanted straight line, the acceleration is constant. This shows a linear relationship. If an object accelerates by a different amount each time period, a graph of its acceleration will not be a straight line. A graph of distance versus time for an accelerating object is curved, and shows a nonlinear relationship. ~Science Explorer Physical Science 21 Use the passage above to help you answer the following questions about acceleration. True/False: If the statement is true, write true. If it is false, change the underlined word or words to make the statement true. ____________________1. If a train is slowing down, it is accelerating. ____________________2. To find the acceleration, you must calculate the change in distance during each unit of time. ____________________3.If an object changes its direction is NOT accelerating. ____________________4. A Ferris wheel turning at a constant speed of 5m/s is not accelerating. ____________________5. If an object is increasing its speed it is accelerating. ____________________6. Graph A plots a race car’s speed for 5 seconds. The car’s rate of acceleration is 6m/s2. ____________________7. Graph B plots the same car’s speed for a different 5-second interval. The car’s acceleration during this interval is 12m/s2. From the passage above below, choose the term that best completes each sentence. Write your answers on the line provided. 8. ______________________occurs when the velocity of an object changes. 9. When you say that a race car traveled northward at 100km/h, you are talking about its _______________________. 10. ______________________ is the distance an object has traveled in a given amount of time. 11. _____________________ is how far an object has traveled. 22 Acceleration Math Problems: Acceleration means a change in speed or direction. It can also be defined as a change in velocity per unit of time. a = Vf-Vi t a=acceleration Vf = velocity final Vi = velocity initial t = time 1. Calculate the acceleration. In order to do this, all time, must have the same unit. a. Initial velocity = 0km/h, Final velocity = 24km/h, Time = 3h List: a= Equation: Substitution: Vf = Vi = t= Answer with units: __________________ b. Initial velocity = 0m/s, Final velocity = 35m/s, Time = 5s List: a= Equation: Substitution: Vf = Vi = t= Answer with units: __________________ c. Initial velocity = 20km/h, Final velocity = 60km/h, Time = 10h List: a= Equation: Substitution: Vf = Vi = t= Answer with units: __________________ 23 d. Initial velocity = 50m/s, Final velocity = 150m/h, Time = 5s List: a= Equation: Substitution: Vf = Vi = t= Answer with units: __________________ e. Initial velocity = 25km/h, Final velocity = 1200km/h, Time = 2min Convert minutes to hours: List: a= Equation: Substitution: Vf = Vi = t= Answer with units: __________________ f. Initial velocity = 90mi/h, Final velocity = 15mi/h, Time = 4s Convert seconds to hours: List: a= Equation: Substitution: Vf = Vi = t= Answer with units: __________________ 24 Force, Mass and Acceleration: Reading Comprehension Read the passage below and define the following vocabulary words: Newton Newton’s 2nd Law of Motion Equation for Force Equation for Acceleration Unit for Force Newton’s second law of motion explains how force, mass and acceleration are related. The net force on an object is equal to the product of its acceleration and its mass. The relationship among force, mass and acceleration can be written in one equation. Force = Mass X Acceleration People often refer to this equation itself as Newton’s second law of motion. When acceleration is measured in meters per second per second (m/s2) and mass is measured in kilograms, force is measure in kilograms X meters per second per second (Kgm/s2). This unit is called the Newton (N) in honor of Sir Isaac Newton. One Newton equals the force required to accelerate one kilogram of mass at 1 meter per second per second. 1N = 1Kg X 1m/s2 Sometimes you may want to write the same relationship among acceleration, force and mass in a different form. Acceleration = Force/Mass The value for acceleration will increase if the value for force increases. According to the equation, acceleration and force change in the same way – both will get larger. The equation also shows that the value for acceleration will increase if the value for mass decrease. Acceleration and mass change in opposite ways. ~ Science Explorer: Physical Science 25 Use the passage above to answer the questions below: 1. Newton’s second law of motion describes the relationship of force, mass, and acceleration. Write the equation. Write the letter of the correct answer on the line. 2. If you increase the mass on an object, its acceleration a. decreases c. stays the same b. also increases d. stops 3. If you increase the force on an object, its acceleration a. decreases c. stays the same b. also increases d. stops 4. If you decrease the mass of an object, it’s acceleration a. decreases c. stays the same b. increases d. stops 5. If you decrease the mass of an object, the force required to accelerate the object at the same rate a. decreases c. stays the same b. increases d. stops Math Problems: equation, list, substitution answer units. 6. How much force is needed to accelerate a 3kg skate board at 5m/s2? List: Equation: F= Substitution: M= Answer & Units: A= How much force is needed to accelerate a 25kg bowling ball at 2m/s2? List: Equation: F= Substitution: M= Answer & Units: A= 7. If a 2Kg bird is pushed by the wind with a force of 2N, how fast does the bird accelerate? List: Equation: F= Substitution: M= Answer & Units: A= 26 II. Newton’s Second Law of Motion: ___________________________________ ____________________________________________________________ a. As an Equation: b. Units of Force: ____________________(____) c. Units of Mass: ____________________ (____) d. Unit’s for Acceleration: __________________ (_______) e. Using Newton’s 2nd Law: 1. A speed boat is pulling a 52kg water skier. The force causes her to accelerate (speed up) at 15m/s2. Calculate the Net Force that causes this acceleration. SHOW WORK: List: F= M= A= Equation: Substitution: Answer & Units: 2. What is the net force on a 1,000kg Elevator accelerating at 2m/s2 ? List: F= M= A= Equation: Substitution: Answer & Units: 3. What Net Force is needed to accelerate a 55kg Cart at 13m/s2? List: F= M= A= Equation: Substitution: Answer & Units: Relationships and Newton’s 2nd Law: At a constant mass (mass remains the same) If the force INCREASES, then the acceleration will ____________________. If the force DECREASES, then the acceleration will ____________________. At a constant force (force remains the same) If the mass INCREASES, then the acceleration will_____________________. If the mass DECREASES, then the acceleration will ____________________. 27 Newton’s 2nd Law Review 1. Newton’s second law of motion describes the relationship of force, mass and acceleration. Write the equation: 2. If you increase the force on an object, its acceleration __________________. 3. If you increase the mass on an object, its acceleration___________________. 4. How much force is needed to accelerate a 42kg bowling ball at 5m/s2? List, Equation, Substitution, Units 5. How much force is needed to accelerate a 6Kg skateboard at 2.3m/s2? List, Equation, Substitution, Units 6. If a 4Kg bird is pushed by the wind with a force of 10N, how fast does the bird accelerate? List, Equation, Substitution, Units Use your notes to prepare for a Newton’s 2nd Law and acceleration quiz!!! 28 Newton’s 3rd Law: Action and Reaction: Reading Comprehension Read the passage below and define the following vocabulary words: Newton’s 3rd Law of Motion Momentum Momentum equation Law of Conservation of Momentum Forces are not “one sided” Whenever one object exerts a force on a second object, the second object exerts a force back on the first object. The force exerted by the second object is equal in strength and opposite in the direction to the first force. Newton called one force the “action” force and the other force the “reaction force”. Newton’s 3rd law of motion describes the relationship between these two forces. Newton’s third law of motion states that if one object exerts a force on another object, then the second objects exerts a force of equal strength in the opposite direction of the first object. For every action there is an equal and opposite reaction. Newton’s third law refers to forces on two different objects. The action and reaction forces described by this law cannot be added together because they are each acting on a different object. Forces can be added together only if they are acting on the same object. The momentum of an object is the product of its mass and its velocity. MOMENTUM = Mass X Velocity The unit of momentum is kilogram-meters per second (kgm/s), since mass is measured in kilograms (kg) and velocity is measured in meters per second (m/s). Like velocity and acceleration, momentum is a vector and described by its direction in addition to its magnitude. The momentum of an object is in the same direction as the velocity of the object. When two objects collide in the absence of friction, momentum is not lost. The law of conservation of momentum states that the total momentum of the objects in an interaction is the same before and after the interaction. The total momentum of any group of objects remains the same unless outside forces act on the objects. Friction would be an example of an outside force that might act on the objects. A quantity that is conserved is the same after an event as it was before the event. ~Science Explorer: Physical Science 29 Notes: III. Newton’s 3rd Law of Motion: ______________________________________ ____________________________________________________________ ____________________________________________________________ a. Examples of Newton’s 3rd law of motion: When someone shoots a gun there is a “kickback”. The gun puts an action force on the bullet propelling it forward and out of the gun, but the bullet then in turn puts a force on the gun which will put a force on the person shooting. This reaction force can cause the person to fall or get a bruise on their arm. Pushing off a wall displays the principles of Newton’s 3rd law. The Ghost puts an action force on the wall. The wall then puts an equal reaction force on the Ghost causing the Ghost to move forward. Without the reaction force the Ghost on the skateboard would not move. 30 Bill Nye – The Science Guy: Momentum Worsheet 1. Whenever something is moving it has ______________________. 2. When moving things run into each other, momentum can ________________. 3. Jai Alai is a sport that originated in what country? _________________ 4. Jai Alai balls have been clocked at approximately ______________ kilometers per hour. 5. The momentum of all the pieces of the ball soaked in liquid nitrogen is equal to the ____________________________ of the bouncing ball. 6. Conservation of _______________________ says that whatever you put into a should be equal to the resulting movement. 6. Rockets move because of the momentum of their __________________. 7. The momentum of the moving rocket and the momentum of the fuel are in movement _______________________ direction(s). (opposite or same) 8. Momentum depends on how much things ________________ and how ______________ they are moving. 31 Momentum – Reading comprehension Read the following passage and answer the questions below…. The sports announcer says, "Going into the all-star break, the Chicago White Sox have the momentum." The headlines declare "Chicago Bulls Gaining Momentum." The coach pumps up his team at half-time, saying "You have the momentum; the critical need is that you use that momentum and bury them in this third quarter." Momentum is a commonly used term in sports. A team that has the momentum is on the move and is going to take some effort to stop. A team that has a lot of momentum is really on the move and is going to be hard to stop. Momentum is a physics term; it refers to the quantity of motion that an object has. A sports team that is on the move has the momentum. If an object is in motion (on the move) then it has momentum. Momentum can be defined as "mass in motion." All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion. The amount of momentum that an object has is dependent upon two variables: how much stuff is moving and how fast the stuff is moving. Momentum depends upon the variables mass and velocity. In terms of an equation, the momentum of an object is equal to the mass of the object times the velocity of the object. Momentum = mass • velocity In physics, the symbol for the quantity momentum is the lower case p. Thus, the above equation can be rewritten as p=m•v where m is the mass and v is the velocity. The equation illustrates that momentum is directly proportional to an object's mass and directly proportional to the object's velocity. The units for momentum would be mass units times velocity units. The standard metric unit of momentum is the kg•m/s. While the kg•m/s is the standard metric unit of momentum, there are a variety of other units that are acceptable (though not conventional) units of momentum. Examples include kg•mi/hr, kg•km/hr, and g•cm/s. In each of these examples, a mass unit is multiplied by a velocity unit to provide a momentum unit. This is consistent with the equation for momentum. Momentum as a Vector Quantity Momentum is a vector quantity. As discussed in an earlier unit, a vector quantity is a quantity that is fully described by both magnitude and direction. To fully describe the momentum of a 5-kg bowling ball moving westward at 2 m/s, you must include information about both the magnitude and the direction of the bowling ball. It is not enough to say that the ball has 10 kg•m/s of momentum; the momentum of the ball is not fully described until information about its direction is given. The direction 32 of the momentum vector is the same as the direction of the velocity of the ball. In a previous unit, it was said that the direction of the velocity vector is the same as the direction that an object is moving. If the bowling ball is moving westward, then its momentum can be fully described by saying that it is 10 kg•m/s, westward. As a vector quantity, the momentum of an object is fully described by both magnitude and direction. The Momentum Equation as a Guide to Thinking From the definition of momentum, it becomes obvious that an object has a large momentum if both its mass and its velocity are large. Both variables are of equal importance in determining the momentum of an object. Consider a Mack truck and a roller skate moving down the street at the same speed. The considerably greater mass of the Mack truck gives it a considerably greater momentum. Yet if the Mack truck were at rest, then the momentum of the least massive roller skate would be the greatest. The momentum of any object that is at rest is 0. Objects at rest do not have momentum - they do not have any "mass in motion." Both variables - mass and velocity - are important in comparing the momentum of two objects. ~ThePhysicsClassroom.com Use the massage above to help fill in the blanks below: 1. If an object is in ________________________ then it has momentum. 2. The amount of momentum depends on what 2 variables? ______________________ and ________________________ 3. The momentum of an object is equal to the _____________________ times the ______________________ of the object. 4. Write the momentum equation: __________________________________ 5. The symbol for moment is _________. 6. What is the standard unit for momentum? __________________ 7. Momentum is a VECTOR quantity (like velocity and force) which means it has a _____________________ (quantity) and a ______________________. 8. The _____________________ of the momentum is the same as the ____________________ of the velocity. 33 9. The greater the _________________ of the truck the ______________ the momentum of the truck. 10. The momentum of any object at rest is ___________, because if an object is at rest then it _______ _______ have momentum because momentum is “_____________ in_____________” MOMENTUM NOTES: Momentum = _____________________________________________ a. Unit for momentum: __________________________________ b. Equation for momentum: _______________________________ b. Conservation of momentum: _________________________________ ____________________________________________________________ ____________________________________________________________ c. Momentum increases when either the ___________________ or the ___________________ increases. 34 Momentum Problems: 1. If the truck has a mass of 2,000 kilograms, what is its momentum? (velocity = 35 m/s) Express your answer in kg·m/sec. List: P= v= m= Equation: Substitution: Answer with units:__________________________ 2. If the car has a mass of 1,000 kilograms, what is its momentum? (v = 35 m/s) List: P= v= m= Equation: Substitution: Answer with units:__________________________ 3. An 8-kilogram bowling ball is rolling in a straight line toward you. If its momentum is 16 kg·m/sec, how fast is it traveling? List: P= v= m= Equation: Substitution: Answer with units:__________________________ 4. A beach ball is rolling in a straight line toward you at a speed of 0.5 m/sec. Its momentum is 0.25 kg·m/sec. What is the mass of the beach ball? List: P= v= m= Equation: Substitution: Answer with units:__________________________ 35 5. A 4,000-kilogram truck travels in a straight line at 10.0 m/sec. What is its momentum? List: P= v= m= Equation: Substitution: Answer with units:__________________________ 6. A 1,400-kilogram car is also traveling in a straight line. Its momentum is equal to that of the truck in the previous question. What is the velocity of the car? List: P= v= m= Equation: Substitution: Answer with units:__________________________ 7. Which has more momentum an 8.0-kilogram ball rolling in a straight line at a speed of 0.2 m/sec or a 4.0-kilogram ball rolling along the same path at a speed of 1.0 m/sec? 8.0kg ball: 4.0kg ball: List: P= v= m= Equation: List: P= v= m= Substitution: Answer with units:__________ Equation: Substitution: Answer with units:__________ ANSWER: _________________________________________________________________________ 8. The momentum of a car traveling in a straight line at 20 m/sec is 24,500 kg·m/sec. What is the car’s mass? List: P= v= m= Equation: Substitution: Answer with units:__________________________ 36 9. A 0.14-kilogram baseball is thrown in a straight line at a velocity of 30 m/sec. What is the momentum of the baseball? List: P= v= m= Equation: Substitution: Answer with units:__________________________ 10. Another pitcher throws the same baseball in a straight line. Its momentum is 2.3 kg·m/sec. What is the velocity of the ball? List: P= v= m= Equation: Substitution: Answer with units:__________________________ 37 Use the passage and your notes to help you answer the following questions: 1. What does it mean to say momentum is conserved?______________________ ____________________________________________________________ ____________________________________________________________ 2. What is Newton’s 3rd Law of motion? ________________________________ ____________________________________________________________ 3. How does the diagram illustrate Newton’s third law of motion? In you answer, compare the force of the foot kicking the soccer ball with the force of the soccer ball on the foot. Once the ball is kicked, in what direction will the force of friction be? ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ___________________________________________________________ 4. What is momentum? ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ MOMENTUM = Mass X Velocity p=MXV p=momentum, m = Mass, v= velocity 5. What is the momentum of a bird with a mass of 0.018kg flying at 15m/s.? List: Equation: _________________________ p= Substitution:_________________________ v= Answer with units:_________________________ m= 6. What is the momentum of a 20kg dog running at a speed of 8m/s. List: Equation: _________________________ p= Substitution:_________________________ v= Answer with units:_________________________ m= 38 7. Which has more momentum: a 3kg sledge hammer swung at 1.5m/s or a 4kg sledge hammer swung at 0.9m/s? Prove mathematically and then write your answer in sentence form. ____________________________________________________________ ____________________________________________________________ 8. A golf ball travels at 16m/s, while a baseball moves at 7m/s. The mass of the golf ball is 0.045kg and the mass of the baseball is 0.14kg. Which has greater momentum? Prove mathematically, then write your answer in sentence form ____________________________________________________________ ____________________________________________________________ 9. Could an elephant have the same momentum as a golf ball? Explain !!!!!Use you notes and the passages above to prepare for a Newton’s Laws and Momentum Quiz!!!!! 39 SIMPLE MACHINES Bill Nye Video 1. What type of a machine is a ramp, lever and pulley?________________________ 2. How do simple machines allow us to change forces? 3. What kind of simple machine is a catapult and what is the pivot point called? 4. What are some examples of levers? 5. What are some simple machines on a bicycle? 6. Why is a ramp better than a ladder and what are the disadvantages of the ramp? 7. Describe a screw and what kind of simple machine is it? 8. What did the boy make the homemade screw out of and who first invented it? 9. What simple machines do cranes use? 10. Why did Bill Nye win the race? 40 Simple Machines – reading comprehension Throughout our history, people have learned ways to increase force, change the direction of force and increase the rate of work. A machine is a device that helps us do these things and in return makes the work easier. We do not know what the first machine was. It may have been the tree branch that prehistoric people used as a lever to move a huge stone, or the sharp rock used as a scraper (wedge) to skin animal hides. Later people discovered the use of logs as rollers. This perhaps encourages the idea for the invention of the wheel and axle. An inclined plane, used by ancient civilizations, was simply a sloping surface. The pulley was a much later invention, as was the screw. The Industrial Revolution, which began in Great Britain in the 1700s, was sparked by the invention of the steam engine. The Industrial Revolution helped bring people into the machine age and vastly increased the availability of many kinds of products. Machines enable people to do work with less muscle effort and with greater speed. Many machines are controlled by computer programs, and many tasks are now performed by robots. Therefore, the present time is often referred to as the computer age. Although a machine produces force and controls the direction of force, it cannot create energy. A machine can never do more work than the energy put into it; it can only transform one kind of energy into another kind. For example, and electric food mixer turns electric energy into mechanical energy. Simple machines like levers, axes, and inclined planes make work easier because they change the direction and the magnitude (amount) of the force. Many machines are complex and contain a number of parts that are meant to work together. No matter how complex they are however, all machines are forms of six simple machines or combinations of them. Scientists have identified six simple machines: the lever, inclined plane, pulley, wheel and axle, wedge, and screw. 41 Levers are used frequently to make work easier. The lever is one of the earliest and simplest machines. The lever is usually a stiff, rigid bar that pivots on a point called a fulcrum. A force is exerted on the bar to move a load. Levers consist of 3 parts and the rigid bar. The effort is the push or pull applied to the lever; the resistance is the weight or load that the lever moves; the fulcrum is the fixed pivot point. Crowbars, scissors, seesaws, brooms, wheelbarrows, bottle openers, nut crackers, shovels, and fishing poles are all examples of levers. The wheel and axel is one of the most important inventions in history. It lifts heavy loads with relatively little effort. The roller, forerunner to the wheel and axle, may have been one of the earliest inventions to help people do work. Several logs placed under a heavy object moved with much less effort. But this was a slow cumbersome process. The logs had to be continually moved from the ground behind the object to the ground in front of the object before it could be moved. The discovery that thin sections of a log could be joined rigidly by a pole or log helped people make a more efficient machine; the wheel and axel. The wheel and axel is basically a modified lever. The center of the axle serves as a fulcrum. This machine transforms the force and motion. The wheel and axel allows more work to be accomplished with less effort. In the wheel and axel machine, the wheel is sometimes replaced with a crank, as in the handle of a pencil sharpener. Gears are special kinds of wheels that transfer force to a different part of the machine. Most gears are made of metal. There are many different sizes and types of gears that are used in many different kinds of machines. The outer rim of the gear has notches called teeth. The teeth of two gears fit together, like the teeth of a zipper, so when one gear turns so does the other. 42 The inclined plane is such a simple machine that people often do not realize it is a simple machine. It can be any slanted surface used to raise a load from a lower level to a higher level. Using an inclined plane may make lifting heavy loads easier because less effort is needed, but using the inclined plane does not make less work. The board a person used to push a wheelbarrow to a higher level, the stairs we use to get to the second floor of a building, and the hand plank passengers use to enter a ship are all inclined planes. The wedge is a form of inclined plane which is used to increase force. A single wedge, having one sloping surface, resembles an inclined plane. Two inclined planes with a common base form a double wedge. Wedges can be used to split things apart. If the wedges of a wedge are sharpened, they can be used to cut things. A knife blade is an example. Wedges are sometimes forced between two things to hold them tightly together. An example of this wedge is a door stop. Other common examples of wedges are nails, pins, plows, and chisels. The screw is another form of an inclined plane. It increases the force. A screw has two parts: the body (cylinder) and the thread (the inclined plane wound around the cylinder). Although the most widely known function of the screw is to fasten, different kinds of screw perform a variety of services. The drill bits used to bore holes in wood, plastics and other materials are screws. A jackscrew is used to lift very heavy objects such as houses and automobiles. An airplane propeller is a screw that drills through the air to reduce friction so a plane can travel through the air with less resistance. A ship or submarine propeller performs the same function in the water. The blades of a fan push air to cool us. In addition to these functions, screws are a very important machine in complex machinery. Almost every machine that is built in parts needs some form of screw to fasten it together. 43 The last simple machine is the pulley. A simple pulley is a grooved wheel firmly attached to an axel. A rope passed over the wheel, fits into the groove so it doesn’t slip off. One end of the rope is attached to a bucket or load. When the other end of the rope is pulled, the load is lifted. This simple pulley gains nothing in force, distance or speed but it changes the direction of the force and therefore makes the work easier. A fixed pulley is a simple pulley fastened to one spot. Flag poles are common fixed pulleys. Unlike a fixed pulley, a movable pulley moves along a rope or wire. It gives a gain in force, but a loss in distance. A compound pulley, also known as a block and tackle, is a combination of fixed and moveable pulleys. The combination of pulleys is called a block and the arrangement of blocks is called a block and tackle. Compound pulleys change the force required and the direction of the force to make the work easier. Painters or window washers using scaffolds, shiphands raising and lowering life boats, and garage mechanics lifting motors from automobiles are common uses of the block and tackle. Many machines in our modern world are compound machines made up of several simple machines. These machines help us by producing a gain in distance, force or speed. An ax is an example of an early compound machine. The handle of the ax is a lever and the head of the ax is a wedge. In a modern compound machine, there are examples of nearly every kind of simple machine. On an automobile, for example, a wheel and axel is used in the body, a lever can be found on the door handle, and there are numerous screws. Machines of the future may have different sources of energy such as solar or nuclear power, but they will still be combinations of simple machines. 44 Using the passage above, answer the questions below: 1. By using machines people can do ____________work in less______________. 2. Simple machines like levers, axes, and inclined planes make work easier because they change the _____________________ and the ____________________ of the force 4. From the reading, what are two simple machines you use today? 5. How many simple machines are there? ______________________ 6. Identify the following descriptions with the correct simple machine: a. slopping surface: ___________________________ b. rope over wheel: ___________________________ c. bar pivoting on fixed point: ___________________ d. spiral inclined plane: ________________________ e. wheel connect to a shaft: ____________________ f. slope tapering to a sharp edge: ________________ 7. Name a simple machine used to do the following activities: a. chop wood: ____________________________________ b. load railroad cars with cargo: _______________________ c. remove tacks: __________________________________ d. fasten pieces of wood together: _____________________ e. reduce friction on rolling objects: ____________________ f. raise and lower a sail: _____________________________ 45 Write the word or words that will make each sentence a true statement. 1. A machine can never do more work than the amount of ______________ put into it. 2. No matter how complex the machines seem, they are all forms of 6 _________________________ ___________________. 3. Simple machines help us make better use of our ________________. 4. A see saw is a common example of a __________________. 5. The handle of a pencil sharpener is like the spoke of a __________________. 6. Gears are wheels with ____________________ that can be used to increase force or speed or to change direction. 7. Using an inclined plane to lift a barrel requires less _________________ over a greater distance. 8. A _________________ is an inclined plane wrapped around a cylinder. 9. A simple ____________________ is a grooved wheel firmly attached to an axel 10. A compound pulley, also known as a _____________________________, is a combination of fixed and moveable pulleys. 11. A ________________________ machine is a combination of more than one simple machine. 46 The six types of simple machines are: Inclined plane, wedge, screw, lever, pulley, wheel and axle 1. An ax is used to chop wood. The metal part chops through the wood, pushing it apart into two smaller sections. Which simple machine is found on the head of this ax? 2. The center of this seesaw is used to balance the board with the seats. The children can easily move up and down without much force. The seesaw is an example of which simple machine? 3. The cap on this water bottle has a spiral shape. When you place it on the bottle and twist, the cap pulls itself toward the bottle. The bottle cap is an example of which simple machine? 4. When you turn the large knob on a door, a rod on the inside releases a latch that holds the door closed. It would be difficult to turn the rod, if the knob wasn't attached to it. The door knob and rod make up which simple machine? 5. A wheel with a rope is used to hoist a flag up to the top of a tall flagpole. This simple machine can also be used to help lift heavy objects with less force. The wheel and rope make up which simple machine? 6. A ramp is used for loading this truck. A mover can pull a cart with a heavy object up the ramp. This is much easier than lifting heavy objects into the truck. Which simple machine is on the back of this truck? 47