* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Document
Relativistic mechanics wikipedia , lookup
Specific impulse wikipedia , lookup
Center of mass wikipedia , lookup
Velocity-addition formula wikipedia , lookup
Hunting oscillation wikipedia , lookup
Faster-than-light wikipedia , lookup
Coriolis force wikipedia , lookup
Fundamental interaction wikipedia , lookup
Newton's theorem of revolving orbits wikipedia , lookup
Classical mechanics wikipedia , lookup
Centrifugal force wikipedia , lookup
Equations of motion wikipedia , lookup
Fictitious force wikipedia , lookup
Jerk (physics) wikipedia , lookup
Modified Newtonian dynamics wikipedia , lookup
Seismometer wikipedia , lookup
Rigid body dynamics wikipedia , lookup
Classical central-force problem wikipedia , lookup
Unit 6 PS Standard PS 5 Drill Panther Copy down the Speeds of Animals MAKE A BAR GRAPH WITH THESE ANIMALS AND THEIR SPEEDS ON IT Animal Name on X axis Pig 11 mph Mouse 8 mph Six-lined race runner 18 mph Elephant 25 mph Moose 35 mph Lion 50 mph BAR GRAPH Panther Drill Copy this equation: This how to figure out your speed in miles per hour 75 ft X 1 mile X 3600 sec your 5280 ft 1 hr Your SPEED Speed = Distance divided by time For us today: ft/sec Unit 6 Motion Motion: movement of an object from a fixed point. Fixed point is called the reference point (this is the starting line) Distance Distance how far something has moved. IE How far you drive in your car. It is only a number or amount. For instance LCHS is exactly 61.3 miles from my door to the parking lot. This is distance. Displacement Displacement: is a distance and a direction. For example to get to the deer stand in the woods I had to walk 1500 yards North west from the road. Total or Final Displacement: change in position from the starting point. LOOK AT EXAMPLE ON THE NEXT SLIDE Total displacement You travel: 6 miles east then 3 miles west 6 miles E 3 miles W Total displacement (distance from where you started) = 6 miles – 3 miles = 3 miles. You am now 3 miles from your house. Panther Drill What is the difference between speed and velocity? Speed Speed: the distance traveled per unit of time. s=d/t Different speeds Speed (s) = distance (d)/time (t) meters/sec Cruise control on a empty road= constant speed Bumper to bumper traffic = changing speed, your speed is fast, then slower, then faster, then slower ect Speed and Velocity Speed: we already know is the distance traveled in a given unit of time. Measured for science in meters per second. Can also be mph Velocity: speed with direction 22 m/sec SE IE: You have to walk 2.8 mph NW from the road into the woods to the deer stand. You are here Speed = 22 mph Velocity = 22 mph North East Speed = 22 mph Velocity = 22 mph NorthWest Who cares? You should. The red case means your butt could be toast!!! Hurricane coming right at us!!!!!! The purple case velocity means surfs up dude!!! Hurricane Fran 1996 Different speeds Constant Speed: when speed is unchanged. like cruise control in the car. Changing speed: speed is not constant or consistent. Like stop and go traffic. Average Speed: used when speed is changing, = s (avg) = Total Distance Traveled Total time spent traveling Different speeds 2 Instantaneous Speed: Speed at any given time, only true at that instant it is observed. Instantaneous Speed Ferrari Enzo 0-60 time 3.3 secs. The speed at any time over that 3.3 seconds would be different. Exit Explain the difference between speed and velocity. Panther Drill If the formula for speed is s=d/t, write down how to find distance and how to find time, using the same equations. t = d/s d = s xd Vid Clip VIDEO Acceleration: (a) the rate of change in velocity per unit of time Acceleration = Velocity(final) - Velocity(original) time Original or Initial Velocity= 20 m/sec Final velocity = 80 m/sec Time = 2 sec a= a= 80m/s – 20m/s 2 sec 60m/s / 2 sec 30 m/sec A car traveling at 60 mph accelerates to 90 mph in 3 seconds. What is the car’s acceleration? Acceleration = Velocity(final) - Velocity(original) time = = 90 mph - 60 mph 3 seconds 30 mph 3 seconds = 10 mph/second Acceleration Units The Unit for Acceleration in science is meters per second per second or m/s2 a = V final – V Initial time m/s s Panther Drill If you are traveling at 4 m/sec and then speed up to 12 m/s in a period of 5 seconds. What is your acceleration Tuesday 2/15 Panther Drill 18 Velocity in m/s 16 14 12 10 8 6 4 2 0 1 2 3 4 5 6 7 8 Seconds Use the graph to find out what is the acceleration between 3 seconds and 7 seconds Extra Credit: What is the slope of the line? PD Answer Acceleration (a) = Vf – Vi Vf = 14 m/s t time = 7 sec – 3 sec = 4sec Vi = 6 m/s 14 – 6 = 8/4 = 2 4 2 m/s Extra Credit Slope: 3–7 6-14 m= (y1-y2) (X1-X2) = -4/-8 m=2 ??QUESTION?? Is the acceleration changing when you look at the graph? Yes At what kind of rate, changing or constant? Constant What do you see when you compare the slope with the acceleration? They are = Slope of the line = the acceleration!!!! Example Joval and Justice pull up to each other at a stop light. They decide to race. The 2 cars accelerate as a traffic light turns green. In 5 seconds, Joval (car 1) goes 0-40km/hr and Justice (car 2) goes 0-50 km/hr. Which car accelerates the fastest? Car 1: Given: Useful Equations Unknown Substitute Evaluate Answer Joval’s Car: Given: WHAT IS GIVEN IN THE PROBLEM Unknown WHAT DO YOU NEED TO FIND OUT? Evaluate Answer DOES THIS MAKE SENSE? Useful Equations a Substitute v f vi t Car 1: Given: Useful Equations Time: 5 sec Vi: 0 Vf: 40 Unknown ACCELERATION a Substitute v f vi t HERE YOU WOULD do calculations Evaluate Answer DOES THIS MAKE SENSE? Car 1: Given: Useful Equations Time: 5 sec Vi: 0 Vf: 40 a Unknown Substitute acceleration a= (40 Evaluate Answer DOES THIS MAKE SENSE? YES v f vi t km/hr-0 km/hr) 5 sec a = 40/5 = 8 km/hr/s Car 1: Given: Useful Equations Time: 5 sec Vi: 0 Vf: 40 a Unknown Substitute acceleration a= (40 v f vi t km/hr-0 km/hr) 5 sec a = 40/5 = 8km/hr/s Evaluate Answer DOES THIS MAKE SENSE? YES You do car #2 What is its acceleration? Panther Drill Define the following: 1. Constant acceleration 2. Changing acceleration 3. Positive acceleration 4. Negative Acceleration Positive and Negative Acceleration Positive acceleration: speeding up Velocity Acceleration Negative acceleration: slowing down Velocity Acceleration Velocity is still in the same direction G r a p h i n g Positive acceleration Negative acceleration The area in red is where constant velocity occurs. Here there is 0 acceleration Velocity m/s 25 20 15 Velocity m/s 10 5 0 1 2 3 4 5 6 7 8 9 10 Seconds 11 Changing Acceleration In changing acceleration the graph is not a straight line with a constant slope. Changing acceleration is speeding up or slowing down. Work Lets check it: Vi = 22 Vf = 22 t = 7 (10-3 sec) 22-22 = 0/7 = 0m/s2 7 Velocity m/s 25 20 15 Velocity m/s 10 5 0 1 2 3 4 5 6 7 8 9 10 11 Seconds Graphing Draw a sketch of positive, negative, constant, and zero acceleration on graph paper. Label each sketch. Make sure you title the sketches and tell me what each axis measures.. Divide the graph paper in into quarters. Put each graph in a separate ¼ of the paper. Exit Assignment Velocity Vs Time 30 25 20 15 Velocity Vs Time 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Circle the area where there is positive, negative, and 0 acceleration. Monday Students will construct time-distance graphs PS 5.6 Represent the linear motion of objects on distance-time graphs. Panther Drill In your own words describe Distance Displacement Speed Velocity 0 speed and 0 Acceleration Constant Speed and Acceleraton Positive (Changing) Acceleration Negative Changing Acceleration PRACTICE On your graph paper graph the following data Compare the speed of the 2 objects on a graph Looks like this Panther Drill #1 D14 I 12 10 s 8 t6 a4 n2 c0 e Describe what type of motion or motions that each graph shows #2 16 1 2 3 Time 4 5 6 V 14 E 12 L 10 O8 C 6 I 4 T 2 Y 0 1 2 3 4 Time 5 6 7 ANSWERS #1) Increasing speed, Constant Rate Speed, would be acceleration if y axis = velocity and not distance #2) Slowing down, negative and changing acceleration Story Graph A student walks 25 ft west in 3 secs Then the student stops and talks to his friends for 5 secs. The student then walks 30 feet west in 6 secs Then the student realizes he will be late for class and then walks a lot faster he travels 100 feet in 5 secs Tues Panther Drill How does the force applied to an object affect its acceleration? Lab pp 58 Text Wednesday Start Car LAb Panther Drill 14 D I s t a n c e 12 10 8 6 4 2 0 1 2 3 4 5 6 7 8 9 10 11 12 Time 1. Write down a few sentences to describe what is happening in the graph. Similar to the graphing exercise yesterday. 13 Preview What is a Force: Push or pull on an object. Examples? Passing a Basketball or Kicking a soccer ball Returning Serve in tennis match Stepping on the brakes Catching Line drive. What affect to you think force applied to an object has on acceleration? What affect to you think force applied to an object has on acceleration of the object? When force is increased in the same direction as the acceleration, then the acceleration increases. When force is applied or increased in the opposite direction acceleration will lessen. When force is applied in another direction besides opposite, acceleration can change because the direction will change and acceleration is a measure of velocity and velocity includes direction. Lab On THURSDAY Get a book and open to pp 58-59 Pre-Lab 1) Write a hypothesis of what you think will happen in the lab. 2) List the 2 forces you will apply to the car to change acceleration and how you apply those forces. 3) On a separate sheet of paper create a data table that looks like this. Monday Panther Drill List 3 things you do to change a objects motion or acceleration Force and Motion As we know force is a push or a pull We also know that forces cause movement. Can an object have more than 1 force acting on it at 1 time? YES What are some examples? Net Force: the total of all forces action on an object Force is represented in a diagram by an arrow. The arrow shows the direction the force is pushing or pulling Net Force ** Remember the force has a number (or magnitude) and a direction** When you have balanced forces, net force = 0. How do you measure force? Force is measured in NEWTONS Newton: force necessary to provide a mass of one kilogram with an acceleration of one meter per second per second. NEWTON = (n) Forces Does applying a force to an object always change velocity? Like we just saw an object can have more than 1 force acting on it and not have the motion or velocity change. Balanced forces: forces of equal size (amount or magnitude) acting on an object in opposite direction that cancel each other out. 10n 10n What force acts on us all the time? GRAVITY Gravity is always holding us down on the earth, and the = force of the ground is pushing us back so we stay planted on the ground. What is this an example of? BALANCED FORCES Gravity pulls an object down, but the object is pushed up by the ground or floor it stands on, so the object does not move this is balanced forces. Unbalanced forces: when 2 or more forces are action on an object that are unequal. The object will move in the direction that the stronger force is pushing it. volunteers Net Force ** Remember the force has a number (or magnitude) and a direction** When you have balanced forces, net force = 0. When you have unbalanced forces net force = a number other than 0, the number can be + or – and has a direction Force Diagrams Force Diagram: the rectangle represents the object being studied. The areas represent the forces acting on that object. If you are jumping in the air, your legs produce a force to overcome gravity the force diagram would look like this: 900 N F net= 412 N 588 N Demo Force Diagram Since the object stopped going downward, the force applied to the object by the spring becomes = to the force of gravity Inertia Inertia: the tendency of an object to resist change in its motion. To get an object to change its motion or velocity a force needs to be applied to greater than the force that is already acting on it. The larger the amount force that is needed to change the motion or velocity of an object the greater the inertia of the object. Which on of these will require the strongest force to change its motion? Bowling ball Which on has the greatest inertia? Bowling ball Which of these has the greatest mass? Bowling ball The more mass an object has, the greater its inertia. NEWTONS LAWS Newton’s 1st law of motion states: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. ALSO KNOWN AS LAW OF INERTIA Any body shoot pool? Newton’s Law in Action What forces are in the break in a game of pool? Cue stick-cue ball Cue ball-Other balls Balls hitting each other Are these forces balanced or unbalanced Unbalanced How does this show the law of inertia? The balls are resting until a greater force of the cue ball makes them move. Tuesday Panther Drill Finish Inertia (5) Pre-Video Quiz (5) Video w/ quiz (25) Post Video Sheet (10 min) Newtons 2nd law Panther Drill Describe the law of inertia. Wed Panther Drill Friction Notes Friction Demo Start Newton’s second law notes Exit ticket Panther Drill 1 Which of the following is a force? A. Acceleration B. Inertia C. Friction D. Velocity 2 Which of the following best describes an objects constant velocity A. Its direction is changing B. Acceleration is positive C. Acceleration is negative D. Acceleration is zero What force that is holding the block in place on the incline? FRICTION Friction: the force that opposes the motion or attempted motion of one surface across another surface. To over come the force of friction and make the block move a stronger force must be applied to the block to create unbalanced forces. Friction What causes it? The sticking together of microscopic bumps on an object. The “sticking together” are called microwelds. The larger the mass of the object the stronger the micro-welds, the more friction there is. Friction depends on mass not contact or surface area Friction Where is the friction greater object A or B? WHY? RAISE YOUR HAND DON’T CALL OUT A B 2 kg 3 kg Lab table 3 KINDS OF FRICTION Static friction: “The frictional force that prevents to surfaces from sliding over or past each other” Stationary or still objects, basically what holds an object from sliding across surface when you push on it. The force you applied was not great enough to overcome the micro-welds. Caused by the force pushing down and up on the object. Micro-welds Explains why more force was required to move the blocks once we added the bars in our demo. 3 KINDS OF FRICTION Sliding Friction: is the force that opposes the motion of 2 surfaces past each other after static friction has been broken. Only on objects moving already. The force of sliding friction is in the opposite direction of the applied force. Applied Force (push) More mass = More Friction Sliding friction Sliding Friction Push the book across the floor Sliding friction occurs as the book’s surface moves across the floor. Sliding friction is the opposite force as your “PUSH”. Will the book keep going if you stop pushing? NO, as the force pushing is stopped, sliding friction slows then stops an object. Then static friction takes over. 3 KINDS OF FRICTION Rolling Friction: The friction between a rolling object and the surface it rolls on. The friction between the rolling tires and the ground is called rolling friction. • • Rolling friction is much less friction than static or sliding friction. That is why it is easier to use a dolly than pushing your kid brother in the box. Start PD 4 Air Resistance • Acts on objects on objects that fall through the air • The force of air resistance is in the opposite direction to the force of gravity • Air resistance affects anything that moves in earth’s atmosphere • Air resistance is pushing up as an object falls due to gravity • Depends on speed, size and shape of object. Air resistance START PD 7 Terminal Velocity • When the forces on the falling object are balanced and the object no longer accelerates • When it falls with a constant speed called the terminal velocity Thursday Panther Drill Sound Travels at a speed of 330 m/s. How long does it take for the sound of thunder to travel 1485 meters? s = d/t t = d/s A) 45 seconds s= 330 m/s B) 4.5 seconds d = 1485 m C) 4900 seconds D) 0.22 seconds t= 1485m/330m/s t= 4.5 seconds SHOW WORK!!!!!! Newton’s nd 2 Law of motion Force and Acceleration The other day we talked about Newton’s first law of motion that basically says that an objects motion can only change if an unbalanced force acts on it. How is a 60 mph fastball different than a 95 mph fastball? DUH the speed right? And the force it is thrown with. Also the acceleration of the faster pitch is greater because its velocity changes more over the same distance EVIDENCE a of 60 mph fastball: Vfin = 60 mph Vin = 0 mph 60 – 0 / 60.5 = .99 m/h2 Distance = 60.5 feet. a of 95 mph fastball Vfin = 90 mph Vin = 0 mph Distance = 60.5 feet. 90 – 0 / 60.5 = 1.49 m/h2 Newton’s 2nd Law of motion Mass and Acceleration If you throw a baseball and shot-put as hard as you can (with the same force) will the move at the same speed? NO!!! WHY? The shot is much heavier (greater mass) and it requires much more force to make it move at the same speed as the baseball Baseball = .14 kg High School Shot = 4 kg NEWTON’S SECOND LAW OF MOTION NEWTON’S SECOND LAW OF MOTION: the acceleration of an object is in the same direction as the net force acting on the object, and the acceleration can be figured out using the following formula: acceleration (in m/s2) = net force (in newtons) mass (in Kg) a= F net m NEWTON’S SECOND LAW OF MOTION You can use the formula to find net force or mass if you know the 2 other variables. F net = m x a F net = net force m = F net a a = acceleration m = mass Force Calculated A rocket engine provides 28,913 Newtons of thrust. The rocket has a mass of 2,350 kilograms. Calculate its acceleration if it moves HORIZONTALLY (we don’t want to fight gravity yet). a= F net m = 28913 N 2350 kg = 12.30 m/s2 YOU TRY 1) Find the mass: You push on a skateboard with a force of 10 N and it accelerates at 1.5 m/s2 What do you have given in the problem? a = 1.5 m/s2 & force 10 N What do you need to find? MASS 6.67 Kg M = Fnet / a ; 10 N/ 1.5 m/s2 = Panther Drill What is Newtons 2nd law? If your net force is 25 newtons and your acceleration is .5 m/s2. What is the mass in kg of the object? More A truck accelerates at 10 m/s2 with a force of 1500 newtons. What is the mass of the truck? Have: a & Fnet Need: mass Formula: m = Fnet/a Solve: m = 1500/10 ANSWER: 150 Kg Friday Problems Newtons 2nd law Tuesday • Gravity Panther Drill 3/8 Define gravity in your own words. Gravity Gravity: an attractive force between any 2 objects, that depends on the mass of the objects and the distance between them. If the mass of one of the objects increases then the of attraction between the 2 objects increases. Gravity As the distance between 2 objects decreases then the gravitational force between them increases. As the distance between 2 objects increases then the gravitational force between them decreases. Gravity Newtons Universal Law of Gravity: (F) gravitational force = G x (m1 x m2) d2 G is a constant m = mass d = distance between the 2 objects. The force of Gravity Lets figure out the force of attraction (gravity between the earth and the moon Distance between the 2: 384,403 km Mass of moon: 7.36 × 1022 kilograms Mass of earth: 5.9742 × 1024 kilograms Set up the equation and we will do the math together. Get w/ your partner Each partner will do one of the questions and then explain their answer to their partner. A/B partner Partner A: The space shuttle launches at 5:00 am. The gravity felt be the astronauts just before launch is 9.8 m/s2. How will the force of gravity felt be different 5 min after launch? Why? Partner B: There are 2 identical satellites orbiting the earth, on at a distance of 120 Km (SAT. A)and on at a distance of 150 km (SAT B). Which satellite feels the earths gravity the strongest? Why? Panther Drill Two teams are competing in a tug-of-war contest. Team A is pulling at 4000N and Team B is pulling at 4900N is the opposite direction. Sketch the forces and show the net force exerted. Which team is winning? Is this force balanced or unbalanced? 4000N g g Team A Team B Rope Ground pushing up 4900N Mass Definition: How much matter something contains Abbreviation: m How it is measured: with a balance. Unit: kilogram (kg) FOR THESE PROBLEMS MASS IS ALWAYS IN KG How to figure out mass (Newton’s 2nd Law: Fnet = mass x acceleration) [Fnet = m x a] Weight • Definition: a force that combines (or puts together) mass and acceleration due to Gravity (ag) or also called the gravitational force on an object. • Abbreviation: W • How it is measured: on a scale. • Unit: Newton (N) • How to figure it out: Weight (W) = mass (m) x acceleration due to gravity (ag) [w=m x ag] Calculations Using the formula W = m x ag we can figure out weight or mass. g (gravity) always equals 9.8 m/s2 ,unless you are on another planet. To find weight multiply mass by gravity [w = m x ag] To find mass divide weight by gravity [m = w/ ag] To find gravity, divide weight by mass [ag = w/m] Thurs Panther Drill #1 What is the formula for determining weight? a) w= ag/m b) w= ag x m c) w= m/ag # 2 If a stone has a mass of 14 kg and it is thrust down at the ground with 2 times the force of gravity, what would be the weight of the object as it fell. 280 N Newtons 3rd Law Remember that when there is an action, there is also a re-action. Think about it like this; when you jump on a trampoline the trampoline exerts a force back at you. Newtons 3rd Law Newton’s 3rd law says, that when 1 object exerts a force on a 2nd object the 2nd object exerts a force that is equal and in the opposite of the 1st force. For every action there is a an = and opposite reaction. So with that being said, does that mean that the forces are balanced? NO Even though the forces are = they are not balanced because they are acting on different objects. Think of a swimmer, as the swimmer moves forward the water pushes back but she still can move. Example Lets try Volunteers Need 2 1 sit in rolling chair and throw the ball HARD to the other person. Look, the ball gets force exerted on it and moves, but you also move a little as the ball exerts a force on you. Think of some other examples. Main example Rockets use Newton’s 3rd law, The engine exerts a force that pushes hot gas out the back of the rocket, the gas exerts a force on the rocket and LIFT OFF What is your weight on other planets Classwork 1. Get your mass in pounds, and convert it to Kg: Your wt in lbs = Your wt in Kg 2.2 256/2.2 = 116.36 2. Determine your mass: Your wt in kg 9.8 116.36/9.8 = 26.12 kg (mass) 3. Determine your weight on other planets: W = m x ag Gravity on other Planets Mercury: 3.73 m/s2 Venus: 8.93 m/s2 Jupiter: 24.92 m/s2 Neptune: 11.67 m/s2 Pluto (planetoid): .784 m/s2 Now that you have your mass figured out determine your weight on the planets above w/ different gravity than on earth Which Newton’s Law applies? A ball gets kicked and rolls along the ground. The ball will continue to roll, at a constant velocity, unless something stops it. 1st law You are standing on a skateboard and push against a wall? You roll in the opposite direction. 3rd law The fact that if you throw a baseball and softball with the same force the baseball will move faster. 2nd law When you are traveling in a car and holding a cup of coffee and the driver slows down fast, and the coffee spills over the front edge of the cup. 1st – Inertia The fact that the moon helps to influence the tides on the planet and the earth keeps the moon from flying away. Newtons law of gravity When a soccer ball is sitting on the ground it will stay there until someone kicks it. 1st law A train starts to pull a long line of boxcars that were sitting at rest. Since the boxcars are so massive, they have a great deal of inertia and it takes a large force to change their motion. Once they are moving, it takes a large force to stop them? 1st law The more force hit the tennis ball with the faster it will go 2nd law Fri Panther Drill What is weight? a) Force an object exerts due to gravity b) The mass of an object c) Acceleration due to gravity What is the difference between static and kinetic friction? a) Static friction holds in place, while kinetic friction only occurs when objects are moving. b) Static and kinetic friction both resist movement, but static requires a stronger force to overcome c) Both a and b. Study Guide Use the book and your notes to complete the study guide.