Download Forces: notes

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.
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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?
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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
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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:
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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 =
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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?
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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.
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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.
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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?
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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!!!!
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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.
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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 ___________________.
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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.
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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?
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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