Question 1

A stationary firecracker explodes, breaking into two parts of equal mass. One part is moving north at 20 m/s. The velocity of the other part is

Accepted Answer

A)   20 m/s with a direction that's impossible to predict without more information.
B)   also northward at 20 m/s.
C)   zero.
D)   southward at 20 m/s.
E)   impossible to predict without more information.

Question 2

A rocket taking off straight upward develops a thrust of 10,000 newtons. The rocket weighs 2,000 newtons. The net force on the rocket, neglecting air resistance, is

Accepted Answer

A)   8,000 newtons.
B)   10,000 newtons.
C)   12, 000 newtons.
D)   2,000 newtons.
E)   zero.

Question 3

You throw a ball straight upward. While it is moving upward, the net force on the ball is

Accepted Answer

A)   zero.
B)   in the downward direction.
C)   in the horizontal direction.
D)   in the upward direction.
E)   directed oppositely to the acceleration.

Question 4

Suppose we subject a golf ball and a more massive lead ball to identical net forces. Then, compared to the golf ball, the lead ball must have

Accepted Answer

A)   a larger acceleration.
B)   a smaller acceleration.
C)   a larger speed.
D)   a smaller speed.
E)   None of the above answers is necessarily true.

Question 5

The basic physical principal principle that explains the operation of rocket engines is

Accepted Answer

A)   the law of force pairs.
B)   the law of inertia.
C)   the atomic hypothesis.
D)   Galileo's principle of falling.
E)   Actually, rockets are unexplainable.

Question 6

Which of the following principles explains why guns recoil?

Accepted Answer

A)   The law of inertia.
B)   Conservation of momentum.
C)   Newton's law of motion.
D)   Conservation of energy.
E)   None of the above.

Question 7

A block of wood is given a brief push and then allowed to slide [without further pushing] along a table top, slowing down as it moves toward the east. As the block slides,

Accepted Answer

A)   its acceleration is toward the east.
B)   its acceleration is toward the west.
C)   the net force on it is zero.
D)   it has no acceleration.
E)   its velocity is toward the west.

Question 8

One- third as much net force is exerted on object A as on object B. The two objects have the same mass. How do their accelerations compare?

Accepted Answer

A)   Object A has three times as much acceleration as object B.
B)   Object A has one- sixth as much acceleration as object B.
C)   Object A has one- third as much acceleration as object B.
D)   They both have the same acceleration.
E)   It is impossible to answer this without further information about the two objects.

Question 9

Are there any kinds of situations in which the momentum of a moving system is not conserved?

Accepted Answer

A)   No, because the momentum of any system is always conserved.
B)   Yes, if there is friction acting between different parts of the system.
C)   Yes, if some of the parts of the system collide with each other.
D)   Yes, if any part of the system is acted upon by forces external to the system.
E)   No, because the law of inertia demands that any moving system must keep moving.

Question 10

You hold a 5- newton rock motionless in your hand. Regarding the forces on this rock,

Accepted Answer

A)   there are no forces of any kind acting on the rock, because it is not moving.
B)   the downward force of gravity is balanced by the upward force of air resistance.
C)   the net force on the rock is 5 newtons, directed upward.
D)   the net force on the rock is 5 newtons, directed downward.
E)   the net force on the rock is zero.

Question 11

A certain grapefruit on Earth has a mass of one kilogram and a weight of one newton. When the grapefruit is on the moon its mass is

Accepted Answer

A)   one kilogram.
B)   less than ten newtons.
C)   ten newtons.
D)   less than one kilogram.

Question 12

Mary pushes horizontally on a large, heavy table which is standing alone in the middle of a room, and notes that the table does not move despite the fact that she is pushing on it (see the figure) . Why doesn't the table move?

Accepted Answer

A)   Very massive objects, such as the table, are difficult to set into motion because of their large inertia.
B)   The table pushes back on Mary with a force that is even larger than Mary's pushing force.
C)   The force of gravity pulls downward on the table, and this force cancels the pushing force.
D)   A frictional force is also exerted by the floor on the table, and this force is equal and opposite to the pushing force.
E)   The table exerts a force on Mary, and this force is equal and opposite to the pushing force.

Exam 4: Why Things Move As They Do

A stationary firecracker explodes, breaking into two parts of equal mass. One part is moving north at 20 m/s. The velocity of the other part is

Correct Answer
verified

Which of the following principles explains why guns recoil?

Correct Answer
verified

A rocket taking off straight upward develops a thrust of 10,000 newtons. The rocket weighs 2,000 newtons. The net force on the rocket, neglecting air resistance, is

Correct Answer
verified

Suppose we subject a golf ball and a more massive lead ball to identical net forces. Then, compared to the golf ball, the lead ball must have

Correct Answer
verified

The basic physical principal principle that explains the operation of rocket engines is

Correct Answer
verified

A certain grapefruit on Earth has a mass of one kilogram and a weight of one newton. When the grapefruit is on the moon its mass is

Correct Answer
verified

Mary pushes horizontally on a large, heavy table which is standing alone in the middle of a room, and notes that the table does not move despite the fact that she is pushing on it (see the figure) . Why doesn't the table move?

Correct Answer
verified

Are there any kinds of situations in which the momentum of a moving system is not conserved?

Correct Answer
verified

One- third as much net force is exerted on object A as on object B. The two objects have the same mass. How do their accelerations compare?

Correct Answer
verified

You throw a ball straight upward. While it is moving upward, the net force on the ball is

Correct Answer
verified

A block of wood is given a brief push and then allowed to slide [without further pushing] along a table top, slowing down as it moves toward the east. As the block slides,

Correct Answer
verified

You hold a 5- newton rock motionless in your hand. Regarding the forces on this rock,

Correct Answer
verified

Exam 4: Why Things Move As They Do

A stationary firecracker explodes, breaking into two parts of equal mass. One part is moving north at 20 m/s. The velocity of the other part is

Correct AnswerverifiedShow Answer

Which of the following principles explains why guns recoil?

Correct AnswerverifiedShow Answer

A rocket taking off straight upward develops a thrust of 10,000 newtons. The rocket weighs 2,000 newtons. The net force on the rocket, neglecting air resistance, is

Correct AnswerverifiedShow Answer

Suppose we subject a golf ball and a more massive lead ball to identical net forces. Then, compared to the golf ball, the lead ball must have

Correct AnswerverifiedShow Answer

The basic physical principal principle that explains the operation of rocket engines is

Correct AnswerverifiedShow Answer

A certain grapefruit on Earth has a mass of one kilogram and a weight of one newton. When the grapefruit is on the moon its mass is

Correct AnswerverifiedShow Answer

Mary pushes horizontally on a large, heavy table which is standing alone in the middle of a room, and notes that the table does not move despite the fact that she is pushing on it (see the figure) . Why doesn't the table move?

Correct AnswerverifiedShow Answer

Are there any kinds of situations in which the momentum of a moving system is not conserved?

Correct AnswerverifiedShow Answer

One- third as much net force is exerted on object A as on object B. The two objects have the same mass. How do their accelerations compare?

Correct AnswerverifiedShow Answer

You throw a ball straight upward. While it is moving upward, the net force on the ball is

Correct AnswerverifiedShow Answer

A block of wood is given a brief push and then allowed to slide [without further pushing] along a table top, slowing down as it moves toward the east. As the block slides,

Correct AnswerverifiedShow Answer

You hold a 5- newton rock motionless in your hand. Regarding the forces on this rock,

Correct AnswerverifiedShow Answer

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