Physical Science: Newton's Laws
NAME _______________________________________
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
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1. The distance traveled by an object divided by the time it takes to travel that distance is called
a. average velocity.
c. average acceleration.
b. average speed.
d. activity.
2. What is the speed of an object at rest?
a. 15 km/h
b. 0 km/h
c. 1 km/h
d. This cannot be determined without further information.
3. The difference between speed and velocity is that velocity includes
a. direction.
c. time.
b. distance.
d. weight.
4. Acceleration is defined as the change in velocity divided by
a. speed.
c. time.
b. final velocity.
d. distance.
5. The SI unit for acceleration is
a. mph.
c. m/s2.
2
b. ft/s .
d. v / t.
6. On a velocity-time graph, a line with a negative slope indicates that the object is
a. speeding up.
c. not moving.
b. slowing down.
d. traveling at a constant speed.
7. When the velocity of an object changes, it is acted upon by a(n)
a. force.
c. momentum.
b. inertia.
d. deceleration.
8. The combination of all of the forces acting on an object is called the
a. total force.
c. super force.
b. union of forces.
d. net force.
9. If the net force on an object is zero then the object has
a. reaction forces.
c. balanced forces.
b. action forces.
d. unbalanced forces.
10. A tug-of-war that results in one team pulling the other across the line is an example of
a. action forces.
c. balanced forces.
b. reaction forces.
d. unbalanced forces.
11. Friction is defined as
a. force that opposes motion between two surfaces that are touching.
b. rate at which velocity changes.
c. resistance of an object to a change in its velocity.
d. speed of an object in a particular direction.
12. If you divide momentum by velocity, the result is the value of the object’s
a. mass.
c. energy.
b. direction.
d. speed.
13. Whenever an object is standing still, which of the following is/are zero?
a. speed.
c. momentum.
b. velocity.
d. All of the above
14. A 10.0 kg dog chasing a rabbit north at 6.0 m/s has a momentum of
a. 0.6 kg m/s.
c. 60.0 m/s.
b. 60.0 kg m/s north.
d. 60.0 kg/s.
____ 15. Weight is best described as
a. an object’s resistance to acceleration.
b. what causes an object to fall.
c. the downward force exerted on objects due to gravity.
d. a force solely dependent on an object’s mass.
____ 16. When objects are moved further apart from each other, the force of gravity
a. increases.
c. decreases.
b. stays the same.
d. decreases at first and then increases.
____ 17. The law that states that every object maintains constant velocity unless acted on by an unbalanced force is
a. Newton’s first law of motion.
c. Newton’s third law of motion.
b. Newton’s second law of motion.
d. the law of conservation of momentum.
____ 18. The law that states that for every action force there is an equal and opposite reaction force is
a. Newton’s first law of motion.
c. Newton’s third law of motion.
b. Newton’s second law of motion.
d. the law of conservation of momentum.
____ 19. The law that states that the unbalanced force acting on an object equals the object’s mass times its acceleration is
a. Newton’s first law of motion.
c. Newton’s third law of motion.
b. Newton’s second law of motion.
d. the law of conservation of momentum.
____ 20. The SI unit of force, named for the scientist who described the relationship between motion and force, is called the
a. newton.
c. curie.
b. einstein.
d. pasteur.
____ 21. When air resistance balances the weight of an object that is falling, the velocity
a. slowly decreases.
c. rapidly increases.
b. remains constant.
d. None of the above
____ 22. Which object does not have momentum?
a. a fish swimming in a pond
c. a rock by the side of the road
b. a feather falling to the ground
d. a boulder rolling down a hill
____ 23. Earth pulls on the moon and holds the moon in its orbit. The moon pulls on Earth with an equal and opposite force.
This is an example of
a. Newton’s first law.
c. Newton’s third law.
b. Newton’s second law.
d. None of the above
____ 24. What is the unbalanced force that slows down a ball rolling across the floor?
a. the force of friction
c. the force of inertia
b. the force of gravity
d. the force of momentum
____ 25. When gravitational forces and air resistance equalize on an object that is falling toward Earth and the object stops
accelerating, what is the velocity of an object called?
a. resultant velocity
c. instantaneous velocity
b. terminal velocity
d. average velocity
Short Answer
26. Rearrange the speed equation to isolate time on the left side of the equation.
27. In your own words, explain the similarities and differences between velocity and acceleration.
28. Distinguish between balanced forces and unbalanced forces.
29. Why is it easier to push a crate over a smooth concrete sidewalk than over grass?
30. List two situations in which friction is helpful or necessary.
31. If a car travels down the highway at a constant speed, are the forces acting on the car balanced or unbalanced?
Explain.
32. A Transair plane is flying east at 275 km/h. A Worldair plane is flying west at 275 km/h. Are the two planes flying
at the same velocity? Explain your answer.
33. Which has greater momentum, a small pick-up truck traveling at 55 km/h or a full-sized bus traveling at the same
speed?
34. A small sports car traveling south collides with a heavy truck traveling north. Both vehicles are going at the same
speed. Describe what happens.
35. A man is standing on a log that is floating in a river. He jumps forward off the log and into the water. Describe the
motion of the log.
Problem
36. During a race, a sprinter increases from 5.0 m/s to 7.5 m/s over a period of 1.25 s. What is the sprinter’s average
acceleration during this period?
37. The winning time for a 500.0 mile race track was 193 minutes. What was the driver’s average speed?
38. Calculate the horizontal force that must be applied to a 1300 kg vehicle to give it an acceleration of 2.6 m/s 2 on a
level road.
Essay
39. It is often recommended that motorists carry a heavy bag of sand in the trunk of their car when driving on slippery
roads. Use the concept of friction to explain why this would be helpful.
40. A tube of air contains a feather and a coin. Both objects are dropped at the same time. The coin falls faster than the
feather. However, when the air is removed from the tube to create a vacuum, both the feather and the coin reach the
bottom at the same time. Explain why this happens.
41. Using Newton’s First Law, explain how/why wearing seat belts saves lives.
42. Explain how a skyrocket works using one of Newton’s laws of motion.
MULTIPLE CHOICE
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SHORT ANSWER
26. ANS:
t = d/v
DIF: 2
REF: 1
OBJ: 4
27. ANS:
Both involve a change over time. However, velocity is the rate of change of the object’s displacement, whereas
acceleration is the rate of change of the object’s velocity.
DIF: 2
REF: 2
OBJ: 1
28. ANS:
Balanced forces combine to produce a net force that is equal to zero, whereas unbalanced forces combine to
produce a net nonzero force that will cause an acceleration.
DIF: 1
REF: 3
OBJ: 1
29. ANS:
On the grass, the crate experiences more friction.
DIF: 2
REF: 3
OBJ: 1
30. ANS:
Answers may vary. Sample answers: When trying to walk or drive on icy sidewalks or streets; between sandpaper
and the wood that you are trying to make smooth; when trying to slow down a vehicle; when parking a vehicle on a
sloped surface; when trying to warm your hands by rubbing them together.
DIF: 2
REF: 3
OBJ: 3
31. ANS:
The forces must be balanced, because the acceleration is zero.
DIF: 2
REF: 3
OBJ: 1
32. ANS:
No. The planes are flying at the same speed, but in different directions. Therefore, the velocities are different.
DIF: 2
33. ANS:
the bus
REF: 1
DIF: 1
REF: 3
34. ANS:
The sports car will be moved north.
OBJ: 3
OBJ: 3
DIF: 2
REF: 3
OBJ: 3
35. ANS:
The log will move in the opposite direction of the man’s jump.
DIF: 2
REF: 3
OBJ: 3
DIF: 2
37. ANS:
2.59 mi/m
REF: 2
OBJ: 3
DIF: 2
38. ANS:
3400 N
REF: 2
OBJ: 3
DIF: 2
REF: 1
OBJ: 3
PROBLEM
36. ANS:
2.0 m/s2
ESSAY
39. ANS:
A heavy weight in the back of a car would increase the force of the rear wheels against the surface of the road,
increasing the friction between the road and the tires. This will make it easier to drive on a slippery road.
DIF: 3
REF: 3
OBJ: 4
40. ANS:
In the first case, the air provides more resistance (friction) to the motion of the feather than to that of the coin, so
the coin falls faster. In a vacuum there is no air to provide resistance to the objects, so only the force of gravity is
acting upon them and they fall at the same rate.
DIF: 3
41. ANS:
REF: 2
OBJ: 2
Whenever the velocity of a car changes, whether by speeding up, slowing down, or changing directions, the car is
accelerating. If a moving car comes to a quick stop, it also experiences a form of acceleration. Your body feels this
acceleration as a push forward because of inertia, which is your body’s resistance to a change in velocity. Shoulder
belts and lap belts hold you in place, counteracting this inertia, and prevent you from being seriously injured or
killed by hitting the dashboard or by flying through the windshield. Used together, they prevent both your upper
and lower body from continuing to move forward. Lap belts alone would keep your lower body in place, but your
upper body could still be driven forward against the steering wheel or dashboard.
DIF: 3
REF: 1
OBJ: 2
42. ANS:
The fuse is ignited, which in turn ignites the gunpowder inside the skyrocket, and the air around the gunpowder
begins to expand rapidly. If the tube containing the gunpowder were tightly sealed on all sides and ends, it would
explode. However, one end of the rocket is not tightly sealed, allowing the hot gases to escape. These escaping
gases create a force in the opposite direction, the forward direction, according to Newton’s third law of motion,
which says that for every action force there is an equal and opposite reaction force.