Cons of Momentum, Gravity, Torque Study Guide
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
1. Two objects with different masses collide and bounce back after an elastic collision. Before the collision, the
two objects were moving at velocities equal in magnitude but opposite in direction. After the collision,
a. the less massive object had gained momentum.
b. the more massive object had gained momentum.
c. both objects had the same momentum.
d. both objects lost momentum.
____
2. A soccer ball collides with another soccer ball at rest. The total momentum of the balls
a. is zero.
c. remains constant.
b. increases.
d. decreases.
____
3. Two skaters stand facing each other. One skater’s mass is 60 kg, and the other’s mass is 72 kg. If the skaters
push away from each other without spinning,
a. the lighter skater has less momentum.
b. their momenta are equal but opposite.
c. their total momentum doubles.
d. their total momentum decreases.
____
4. Two swimmers relax close together on air mattresses in a pool. One swimmer’s mass is 48 kg, and the other’s
mass is 55 kg. If the swimmers push away from each other,
a. their total momentum triples.
c. their total momentum doubles.
b. their momenta are equal but opposite.
d. their total momentum decreases.
____
5. In a two-body collision,
a. momentum is always conserved.
b. kinetic energy is always conserved.
c. neither momentum nor kinetic energy is conserved.
d. both momentum and kinetic energy are always conserved.
____
6. The law of conservation of momentum states that
a. the total initial momentum of all objects interacting with one another usually equals the total
final momentum.
b. the total initial momentum of all objects interacting with one another does not equal the total
final momentum.
c. the total momentum of all objects interacting with one another is zero.
d. the total momentum of all objects interacting with one another remains constant regardless
of the nature of the forces between the objects.
____
7. Which of the following statements about the conservation of momentum is not correct?
a. Momentum is conserved for a system of objects pushing away from each other.
b. Momentum is not conserved for a system of objects in a head-on collision.
c. Momentum is conserved when two or more interacting objects push away from each other.
d. The total momentum of a system of interacting objects remains constant regardless of forces
between the objects.
____
8. Two objects move separately after colliding, and both the total momentum and total kinetic energy remain
constant. Identify the type of collision.
a. elastic
b. nearly elastic
____
c. inelastic
d. perfectly inelastic
9. Two objects stick together and move with a common velocity after colliding. Identify the type of collision.
a. elastic
c. inelastic
b. nearly elastic
d. perfectly inelastic
____ 10. After colliding, objects are deformed and lose some kinetic energy. Identify the type of collision.
a. elastic
c. inelastic
b. nearly elastic
d. perfectly inelastic
____ 11. Two billiard balls collide. Identify the type of collision.
a. elastic
c. inelastic
b. nearly elastic
d. perfectly inelastic
____ 12. Two balls of dough collide and stick together. Identify the type of collision.
a. elastic
c. inelastic
b. nearly elastic
d. perfectly inelastic
____ 13. In an inelastic collision between two objects with unequal masses,
a. the total momentum of the system will increase.
b. the total momentum of the system will decrease.
c. the kinetic energy of one object will increase by the amount that the kinetic energy of the
other object decreases.
d. the momentum of one object will increase by the amount that the momentum of the other
object decreases.
____ 14. A billiard ball collides with a stationary identical billiard ball in an elastic head-on collision. After the collision,
which of the following is true of the first ball?
a. It maintains its initial velocity.
c. It comes to rest.
b. It has one-half its initial velocity.
d. It moves in the opposite direction.
____ 15. A billiard ball collides with a second identical ball in an elastic head-on collision. What is the kinetic energy of
the system after the collision compared with the kinetic energy before the collision?
a. unchanged
c. two times as great
b. one-fourth as great
d. four times as great
____ 16. Which of the following best describes the momentum of two bodies after a two-body collision if the kinetic
energy of the system is conserved?
a. must be less
c. might also be conserved
b. must also be conserved
d. is doubled in value
____ 17. Tides are caused by
a. differences in the gravitational force of the sun at different points on Earth.
b. differences in the gravitational force of the moon at different points on Earth.
c. differences in Earth’s gravitational field strength at different points on Earth’s surface.
d. fluctuations in the gravitational attraction between Earth and the moon.
____ 18. Why does an astronaut weigh less on the moon than on Earth?
a. The astronaut has less mass on the moon.
b. The astronaut is farther from Earth’s center when he or she is on the moon.
c. The gravitational field strength is less on the moon’s surface than on Earth’s surface.
d. The astronaut is continually in free fall because the moon orbits Earth.
____ 19. If you lift an apple from the ground to some point above the ground, the gravitational potential energy in the
system increases. This potential energy is stored in
a. the apple.
b. Earth.
c. both the apple and Earth.
d. the gravitational field between Earth and the apple.
____ 20. An object’s tendency to resist acceleration is measured by the object’s
a. gravitational mass.
c. gravitational field strength.
b. inertial mass.
d. weight.
____ 21. The degree to which an object attracts other objects is measured by the object’s
a. gravitational mass.
c. gravitational field strength.
b. inertial mass.
d. weight.
____ 22. In this text, which of the following symbols represents gravitational field strength?
a. F
c. g
b. G
d. F
____ 23. In this text, which of the following symbols represents the constant of universal gravitation?
a. F
c. g
b. G
d. F
____ 24. Which of the following equations expresses Newton’s law of universal gravitation?
a.
c.
b.
d.
____ 25. When calculating the gravitational force between two extended bodies, you should measure the distance
a. from the closest points on each body.
b. from the most distant points on each body.
c. from the center of each body.
d. from the center of one body to the closest point on the other body.
____ 26. The gravitational force between two masses is 36 N. What is the gravitational force if the distance between them
is tripled? (G = 6.673  10
Nm /kg )
a. 4.0 N
c. 18 N
b. 9.0 N
d. 27 N
____ 27. Two small masses that are 10.0 cm apart attract each other with a force of 10.0 N. When they are 5.0 cm apart,
these masses will attract each other with what force?
(G = 6.673  10
Nm /kg )
a. 5.0 N
c. 20.0 N
b. 2.5 N
d. 40.0 N
____ 28. Until the middle of the 16th century, most people believed ____ was at the center of the universe.
a. Earth
c. the sun
b. the moon
d. a black hole
____ 29. Which of the following quantities measures the ability of a force to rotate or accelerate an object around an axis?
a. axis of rotation
b. lever arm
c. tangential force
d. torque
____ 30. Where should a force be applied on a lever arm to produce the most torque?
a. closest to the axis of rotation
b. farthest from the axis of rotation
c. in the middle of the lever arm
d. It doesn’t matter where the force is applied.
____ 31. If you want to open a swinging door with the least amount of force, where should you push on the door?
a. close to the hinges
c. as far from the hinges as possible
b. in the middle
d. It does not matter where you push.
____ 32. If you cannot exert enough force to loosen a bolt with a wrench, which of the following should you do?
a. Use a wrench with a longer handle.
b. Tie a rope to the end of the wrench and pull on the rope.
c. Use a wrench with a shorter handle.
d. You should exert a force on the wrench closer to the bolt.
____ 33. Suppose a doorknob is placed at the center of a door. Compared with a door whose knob is located at the edge,
what amount of force must be applied to this door to produce the torque exerted on the other door?
a. one-half as much
c. one-fourth as much
b. two times as much
d. four times as much
____ 34. A heavy bank-vault door is opened by the application of a force of 3.0  10 N directed perpendicular to the
plane of the door at a distance of 0.80 m from the hinges. What is the torque?
a. 120 Nm
c. 300 Nm
b. 240 Nm
d. 360 Nm
____ 35. If the torque required to loosen a nut on a wheel has a magnitude of 40.0 Nm and the force exerted by a
mechanic is 133 N, how far from the nut must the mechanic apply the force?
a. 1.20 m
c. 30.1 cm
b. 15.0 cm
d. 60.2 cm
____ 36. What kind of simple machine are you using if you pry a nail from a board with the back of a hammer?
a. a wedge
c. a lever
b. a pulley
d. a screw