Question 1

A golf ball is struck by a golf club and falls on a green eight feet above the tee. The potential energy of the Earth-ball system is greatest:

Accepted Answer

A)  just before the ball is struck 
B)  just after the ball is struck 
C)  just after the ball lands on the green 
D)  when the ball comes to rest on the green 
E)  when the ball reaches the highest point in its flight 
A)  just before the ball is struck 
B)  just after the ball is struck 
C)  just after the ball lands on the green 
D)  when the ball comes to rest on the green 
E)  when the ball reaches the highest point in its flight E

Question 2

Suppose that the fundamental dimensions are taken to be: force (F), velocity (V) and time (T). The dimensions of potential energy are then:

Accepted Answer

A)  F/T 
B)  FVT 
C)  FV/T 
D)  F/T2 
E)  FV2/T2 
A)  F/T 
B)  FVT 
C)  FV/T 
D)  F/T2 
E)  FV2/T2 B

Question 3

The diagram shows a plot of the potential energy as a function of x for a particle moving along the x axis. The points of neutral equilibrium are:

Accepted Answer

A)  only a 
B)  only b 
C)  only c 
D)  only d 
E)  b and d 
A)  only a 
B)  only b 
C)  only c 
D)  only d 
E)  b and d C

Question 4

An elevator is rising at constant speed. Consider the following statements: I. the upward cable force is constant
II. the kinetic energy of the elevator is constant
III. the gravitational potential energy of the Earth-elevator system is constant
IV. the acceleration of the elevator is zero
V. the mechanical energy of the Earth-elevator system is constant

Accepted Answer

A)  all five are true 
B)  only II and V are true 
C)  only IV and V are true 
D)  all but III are true 
E)  only I, II, and IV are true 
A)  all five are true 
B)  only II and V are true 
C)  only IV and V are true 
D)  all but III are true 
E)  only I, II, and IV are true

Question 5

Two particles interact by conservative forces. In addition, an external force acts on each particle. They complete round trips, ending at the points where they started. Which of the following must have the same values at the beginning and end of this trip?

Accepted Answer

A)  a total kinetic energy of the two-particle system 
B)  the potential energy of the two-particle system 
C)  the mechanical energy of the two-particle system 
D)  the total linear momentum of the two-particle system 
E)  none of the above 
A)  a total kinetic energy of the two-particle system 
B)  the potential energy of the two-particle system 
C)  the mechanical energy of the two-particle system 
D)  the total linear momentum of the two-particle system 
E)  none of the above

Question 6

A 6.0-kg block is released from rest 80 m above the ground. When it has fallen 60 m its kinetic energy is approximately:

Accepted Answer

A)  4700 J 
B)  3500 J 
C)  1200 J 
D)  120 J 
E)  60 J 
A)  4700 J 
B)  3500 J 
C)  1200 J 
D)  120 J 
E)  60 J

Question 7

The diagram shows a plot of the potential energy as a function of x for a particle moving along the x axis. The points of unstable equilibrium are:

Accepted Answer

A)  only a 
B)  only b 
C)  only c 
D)  only d 
E)  b and d 
A)  only a 
B)  only b 
C)  only c 
D)  only d 
E)  b and d

Question 8

The diagram shows a plot of the potential energy as a function of x for a particle moving along the x axis. The points of stable equilibrium are:

Accepted Answer

A)  only a 
B)  only b 
C)  only c 
D)  only d 
E)  b and d 
A)  only a 
B)  only b 
C)  only c 
D)  only d 
E)  b and d

Question 9

A stationary mass m = 1.3 kg is hanging from a spring of spring constant k = 1200 N/m. You raise the mass a distance of 10 cm above its equilibrium position. How much has the potential energy of the mass-spring system changed?

Accepted Answer

A)  1.3 J 
B)  6.0 J 
C)  7.3 J 
D)  12 J 
E)  13 J 
A)  1.3 J 
B)  6.0 J 
C)  7.3 J 
D)  12 J 
E)  13 J

Question 10

As a particle moves along the x axis it is acted by a conservative force. The potential energy is shown below as a function of the coordinate x of the particle. Rank the labeled regions according to the magnitude of the force, least to greatest.

Accepted Answer

A)  AB, BC, CD 
B)  AB, CD, BC 
C)  BC, CD, AB 
D)  BC, AB, CD 
E)  CD, BC, AB 
A)  AB, BC, CD 
B)  AB, CD, BC 
C)  BC, CD, AB 
D)  BC, AB, CD 
E)  CD, BC, AB

Question 11

A force of 10 N holds an ideal spring with a 20-N/m spring constant in compression. The potential energy stored in the spring is:

Accepted Answer

A)  0.5 J 
B)  2.5 J 
C)  5 J 
D)  10 J 
E)  200 J 
A)  0.5 J 
B)  2.5 J 
C)  5 J 
D)  10 J 
E)  200 J

Question 12

The energy of a system increases at a rate of 3.5 t + 6.2 t2, in joules. What is the instantaneous power at t = 3.1 s?

Accepted Answer

A)  3.5 W 
B)  6.2 W 
C)  16 W 
D)  42 W 
E)  70 W 
A)  3.5 W 
B)  6.2 W 
C)  16 W 
D)  42 W 
E)  70 W

Question 13

An ideal spring is used to fire a 15.0-g block horizontally. The spring has a spring constant of 20 N/m and is initially compressed by 7.0 cm. The kinetic energy of the block as it leaves the spring is:

Accepted Answer

A)  0 J 
B)  2.5 *10-2 J 
C)  4.9 * 10-2 J 
D)  9.8 * 10-2 J 
E)  1.4 J 
A)  0 J 
B)  2.5 *10-2 J 
C)  4.9 * 10-2 J 
D)  9.8 * 10-2 J 
E)  1.4 J

Question 14

A 2-kg block is thrown upward from a point 20 m above the Earth's surface. At what height above Earth's surface will the gravitational potential energy of the Earth-block system have increased by 500 J?

Accepted Answer

A)  5 m 
B)  25 m 
C)  46 m 
D)  70 m 
E)  270 m 
A)  5 m 
B)  25 m 
C)  46 m 
D)  70 m 
E)  270 m

Question 15

The graphs below show the magnitude of the force on a particle as the particle moves along the positive x axis from the origin to x = x1. The force is parallel to the x axis and is conservative. The maximum magnitude F1 has the same value for all graphs. Rank the situations according to the change in the potential energy associated with the force, least (or most negative) to greatest (or most positive).

Accepted Answer

A)  3, 1, 2 
B)  1, 3, 2 
C)  2, 3, 1 
D)  3, 2, 1 
E)  2, 1, 3 
A)  3, 1, 2 
B)  1, 3, 2 
C)  2, 3, 1 
D)  3, 2, 1 
E)  2, 1, 3

Question 16

The string in the figure is 50 cm long. When the ball is released from rest, it swings along the dotted arc. How fast is it going at the lowest point in its swing?

Accepted Answer

A)  2.0 m/s 
B)  2.2 m/s 
C)  3.1 m/s 
D)  4.4 m/s 
E)  6.0 m/s 
A)  2.0 m/s 
B)  2.2 m/s 
C)  3.1 m/s 
D)  4.4 m/s 
E)  6.0 m/s

Question 17

The thermal energy of a system consisting of a thrown ball, Earth, and the air is most closely associated with:

Accepted Answer

A)  the gravitational interaction of the Earth and the ball 
B)  the kinetic energy of the ball as a whole 
C)  motions of the individual particles within the ball 
D)  motions of individual particles within the ball and the air 
E)  the kinetic energy of Earth as a whole 
A)  the gravitational interaction of the Earth and the ball 
B)  the kinetic energy of the ball as a whole 
C)  motions of the individual particles within the ball 
D)  motions of individual particles within the ball and the air 
E)  the kinetic energy of Earth as a whole

Question 18

A 5-kg projectile is fired over level ground with a velocity of 200 m/s at an angle of 25  $\degree$ above the horizontal. Just before it hits the ground its speed is 150 m/s. Over the entire trip the change in the thermal energy of the projectile and air is:

Accepted Answer

A)  +6300 J 
B)  -6300 J 
C)  +44,000 J 
D)  -44,000 J 
E)  0 J 
A)  +6300 J 
B)  -6300 J 
C)  +44,000 J 
D)  -44,000 J 
E)  0 J

Question 19

A projectile of mass 0.50 kg is fired with an initial speed of 10 m/s at an angle of 60  $\degree$ above the horizontal. The potential energy of the projectile-Earth system when the projectile is at its highest point (relative to the potential energy when the projectile is at ground level) is:

Accepted Answer

A)  25 J 
B)  18.75 J 
C)  12.5 J 
D)  6.25 J 
E)  none of these 
A)  25 J 
B)  18.75 J 
C)  12.5 J 
D)  6.25 J 
E)  none of these

Question 20

The long pendulum shown is drawn aside until the ball has risen 0.5 m. It is then given an initial speed of 3.0 m/s. The speed of the ball at its lowest position is:

Accepted Answer

A)  0 m/s 
B)  0.89 m/s 
C)  3.1 m/s 
D)  3.7 m/s 
E)  4.3 m/s 
A)  0 m/s 
B)  0.89 m/s 
C)  3.1 m/s 
D)  3.7 m/s 
E)  4.3 m/s

Exam 8: Potential Energy and Conservation of Energy

A golf ball is struck by a golf club and falls on a green eight feet above the tee. The potential energy of the Earth-ball system is greatest:

Suppose that the fundamental dimensions are taken to be: force (F), velocity (V) and time (T). The dimensions of potential energy are then:

The diagram shows a plot of the potential energy as a function of x for a particle moving along the x axis. The points of neutral equilibrium are:

Two particles interact by conservative forces. In addition, an external force acts on each particle. They complete round trips, ending at the points where they started. Which of the following must have the same values at the beginning and end of this trip?

A 6.0-kg block is released from rest 80 m above the ground. When it has fallen 60 m its kinetic energy is approximately:

The diagram shows a plot of the potential energy as a function of x for a particle moving along the x axis. The points of unstable equilibrium are:

The diagram shows a plot of the potential energy as a function of x for a particle moving along the x axis. The points of stable equilibrium are:

A stationary mass m = 1.3 kg is hanging from a spring of spring constant k = 1200 N/m. You raise the mass a distance of 10 cm above its equilibrium position. How much has the potential energy of the mass-spring system changed?

As a particle moves along the x axis it is acted by a conservative force. The potential energy is shown below as a function of the coordinate x of the particle. Rank the labeled regions according to the magnitude of the force, least to greatest.

A force of 10 N holds an ideal spring with a 20-N/m spring constant in compression. The potential energy stored in the spring is:

The energy of a system increases at a rate of 3.5 t + 6.2 t2, in joules. What is the instantaneous power at t = 3.1 s?

An ideal spring is used to fire a 15.0-g block horizontally. The spring has a spring constant of 20 N/m and is initially compressed by 7.0 cm. The kinetic energy of the block as it leaves the spring is:

A 2-kg block is thrown upward from a point 20 m above the Earth's surface. At what height above Earth's surface will the gravitational potential energy of the Earth-block system have increased by 500 J?

The string in the figure is 50 cm long. When the ball is released from rest, it swings along the dotted arc. How fast is it going at the lowest point in its swing?

The thermal energy of a system consisting of a thrown ball, Earth, and the air is most closely associated with:

A 5-kg projectile is fired over level ground with a velocity of 200 m/s at an angle of 25 °\degree° above the horizontal. Just before it hits the ground its speed is 150 m/s. Over the entire trip the change in the thermal energy of the projectile and air is:

A projectile of mass 0.50 kg is fired with an initial speed of 10 m/s at an angle of 60 °\degree° above the horizontal. The potential energy of the projectile-Earth system when the projectile is at its highest point (relative to the potential energy when the projectile is at ground level) is:

The long pendulum shown is drawn aside until the ball has risen 0.5 m. It is then given an initial speed of 3.0 m/s. The speed of the ball at its lowest position is:

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The energy of a system increases at a rate of 3.5 t + 6.2 t², in joules. What is the instantaneous power at t = 3.1 s?

A 5-kg projectile is fired over level ground with a velocity of 200 m/s at an angle of 25 $\degree$ above the horizontal. Just before it hits the ground its speed is 150 m/s. Over the entire trip the change in the thermal energy of the projectile and air is:

A projectile of mass 0.50 kg is fired with an initial speed of 10 m/s at an angle of 60 $\degree$ above the horizontal. The potential energy of the projectile-Earth system when the projectile is at its highest point (relative to the potential energy when the projectile is at ground level) is: