1. Newton’s 3 Laws Review
Name: _______________________
Date: _______________________
Period: ___________
Know the following information and be able to answer the questions on pages 576 – 577.
Newton’s Laws
Write each of his laws below in the space provided.
Law #1: An object in motion stays in motion and an object at rest will stay at rest unless an
unbalanced force acts upon it. – Inertia, balanced and unbalanced forces, friction
Law #2: Objects in motion will continue to travel in the direction of the unbalanced force. – gravity,
weight, acceleration, force, F = M x A
Law #3: For every action force there is an equal and opposite reaction force acting against the action
force. Action and reaction forces
Instructions: Each of the items below is best represented by one of the Newton’s Laws of Motion.
Write a 1, 2 or 3 for each of the following to indicate whether it’s Newton’s 1st
, 2nd
or 3rd
law.
1. __3___A climber pulls down on a rope causing his body to lift upward and rise along the rope.
2. __2___Force= Mass x Acceleration
3. __1___Two bumper cars collide into each other and each car jolts backwards
4. __2___When you give your friend a lift on your bike you have to pedal harder and faster to keep the
same speed (acceleration) as you had when you were on your bike alone
5. __3___For every action there is an equal and opposite reaction.
6. __2___A smaller cannon ball leaves a cannon much faster than a larger, heavier cannon ball fired at
the same time.
7. __1___When you are standing in a subway train and the train suddenly stops but your body
continues to move forward.
8. __2___It is much easier to carry your backpack when it is empty rather than when it’s full of
textbooks.
9. __1___A boy is going down a slide. As he reaches the bottom, friction causes him to slow down and
stop.
2. Vocabulary
Write the vocabulary word on the blank.
1. __Centripetal Force any force that keeps an object moving in a circle
2. __Net Force when all the forces are combined together
3. __Gravity the force of attraction between two masses
4. __Contact Force when one object pushes or pulls another object by touching it
5. __Force a push or a pull
6. __Friction a force that resists motion and brings almost everything to a stop
7. __Inertia the resistance of an object to a change in the speed or the direction
of its motion
8. __Balanced Forces the effects of forces that cancel each other out and result in no
change in motion of the object
9. __Unbalanced Forces the effects that together result in a net force greater than zero and
there is a change in motion of the object
10. __9.8 m/s2
gravitational force on an object
Circle the correct word or phrase
1. More force will give an object (more/less) acceleration.
2. You have two balls and one is more massive than the other. The more massive ball will have
(greater/less) acceleration. (…given that the force remains the same.)
3. When one object exerts a force on another object, the second object exerts a force back that is
(equal in size and opposite in direction/equal in size and in the same direction.)
4. Balanced forces act on (two different objects/the same object).
5. Action/reaction force pairs act on (two different objects/the same object).
6. The more (mass/speed) an object has, the harder it is to accelerate.
Short Answer/Diagrams
Answer the following questions.
1. Using two arrows show an unbalanced force. 65N (300kg) 15N
a. Does motion occur? Yes
b. In what direction? In the direction of the greater force
c. What is the Net Force amount? 65 – 15 = __50__N
d. Why subtract the 15 N? The force is in the opposite direction of the greater force.
3. 2. Using two arrows show a balanced force. 65N (300kg) 65N
a. Does motion occur? No
b. In what direction? The two forces are equal and cancel each other out.
c. What is the Net Force amount? 65 –__65_____ = __0___N
d. Why subtract ? The two forces are in the opposite direction.
3. Using two arrows show an unbalanced force. 65N
15N
a. Does motion occur? Yes
b. In what direction? The object will move in the direction of the applied force.
c. What is the Net Force amount? 65 ( + , - ) __15___ = __80_N
d. Why (add, subtract) ? The two forces are applied toward the same direction and are
working together.
4. Does gravity affect everything? How do you know?
Yes. If gravity did not affect something then the no force would be needed to lift.
5. If the net force on an object is zero, what can you tell about the forces acting on it?
For a net force to be zero, either the forces acting on an object are each 0 Newtons, or their
combined forces are opposing each other and cancel to 0 Newtons.
Formulas
1. What is the formula for force? F = M x A
a. What does each variable stand for?
F = force M = mass A = acceleration
2. What is the unit for:
a. Mass _Kg__
b. Force _N____
c. Acceleration _m/s2
___
3. Practice Problems:
a. What force is needed to accelerate a 10 kg skateboard at 2 m/s2
F = MA so Force = 10 x 2 F = 20 N
b. What acceleration results from a net force of 25N on a 50kg object?
F = MA so F/M = A 25/50 = A 0.5 m/s2
c. What weight is an object when its mass is 40kg?
W = MG G is the acceleration of gravity. W = 40 x 9.8 W = 392 kg·m/s2
d. What is the mass of an object that accelerates to 5m/s2
under a force of 32N?
F = MA so F/A = M 32/5 = M 6.4 kg = M
(300kg)
4. True or False
Write true or false on the blank.
__false__ 1. If you increase the mass on an item without increasing the force you increase the
acceleration.
__true____ 2. If you increase the force on an item without changing the mass you increase
acceleration.
__false__ 3. A force can’t make an object change direction. (Newton’s Second Law)
__false__ 4. Forces can NEVER cause acceleration. (Think balanced or unbalanced forces?)
__false__ 5. If an object only changes direction then it is not accelerating.
__true____ 6. If you drop a ball from a second story building the earth pulls on the ball and the ball
pulls on the earth.
