Question 1

A block slides across a rough horizontal table top. The work done by friction changes:

Accepted Answer

A)   only the kinetic energy
B)   only the potential energy
C)   only the thermal energy
D)   only the kinetic and potential energies
E)   only the kinetic and thermal energies

Question 2

A 700-N man jumps out of a window into a fire net 10 m below. The net stretches 2 m before bringing the man to rest and tossing him back into the air. The maximum potential energy of the net, compared to its unstretched potential energy, is:

Accepted Answer

A)   300 J
B)   710 J
C)   850 J
D)   7000 J
E)   8400 J

Question 3

A particle moves along the x axis under the influence of a stationary object. The net force on the particle, which is conservative, is given by F = (8N/m3) x3. If the potential energy is taken to be zero for x = 0 then the potential energy is given by:

Accepted Answer

A)   (2 J/m4) x4
B)   (-2 J/m4) x4
C)   (24 J/m2) x2
D)   (-24 J/m2) x2
E)   5 J - (2 J/m4) x4

Question 4

A good example of kinetic energy is provided by:

Accepted Answer

A)   a wound-up clock spring
B)   the raised weights of a grandfather's clock
C)   a tornado
D)   a gallon of gasoline
E)   an automobile storage battery

Question 5

Only if a force on a particle is conservative:

Accepted Answer

A)   does it do no work when the particle moves exactly once around any closed path
B)   does the work it does equal the change in the kinetic energy of the particle
C)   does it obey Newton's second law
D)   does it obey Newton's third law
E)   it is not a frictional force

Question 6

A 0.50-kg block attached to an ideal spring with a spring constant of 80 N/m oscillates on a horizontal frictionless surface. The total mechanical energy is 0.12 J. The greatest extension of the spring from its equilibrium length is:

Accepted Answer

A)   1.5 * 10-3 m
B)   3.0 * 10-3 m
C)   0.039 m
D)   0.055 m
E)   18 m

Question 7

The potential energy of a 0.20-kg particle moving along the x axis is given by U(x)  =(8.0 J/m2) x2 + (2.0 J/m4) x4.
When the particle is at x = 1.0 m it is traveling in the positive x direction with a speed of 5.0 m/s. It next stops momentarily to turn around at x =

Accepted Answer

A)   0 m
B)   -1.1 m
C)   1.1 m
D)   -2.3 m
E)   2.3 m

Question 8

A body at rest in a system is capable of doing work if:

Accepted Answer

A)   the potential energy of the system is positive
B)   the potential energy of the system is is negative
C)   it is free to move in such a way as to decrease its kinetic energy
D)   it is free to move in such a way as to decrease the potential energy of the system
E)   it is free to move in such a way as to increase the potential energy of the system

Question 9

A ball is held at a height H above a floor. It is then released and falls to the floor. If air resistance can be ignored, which of the five graphs below correctly gives the mechanical energy E of the Earth-ball system as a function of the altitude y of the ball?

Accepted Answer

A)   I
B)   II
C)   III
D)   IV
E)   V

Question 10

A 2.2-kg block starts from rest on a rough inclined plane that makes an angle of 25   °\degree°  with the horizontal. The coefficient of kinetic friction is 0.25. As the block goes 2.0 m down the plane, the mechanical energy of the Earth-block system changes by:

Accepted Answer

A)   0 J
B)   -9.8 J
C)   9.8 J
D)   -18 J
E)   18 J

Question 11

Which of the five graphs correctly shows the potential energy of a spring as a function of its elongation x?

Accepted Answer

A)   I
B)   II
C)   III
D)   IV
E)   V

Question 12

A small object of mass m, on the end of a light cord, is held horizontally at a distance r from a fixed support as shown. The object is then released. What is the tension in the cord when the object is at the lowest point of its swing?

Accepted Answer

A)   mg/2
B)   mg
C)   2 mg
D)   3 mg
E)   mgr

Question 13

A 0.50-kg block attached to an ideal spring with a spring constant of 80 N/m oscillates on a horizontal frictionless surface. The total mechanical energy is 0.12 J. The greatest speed of the block is:

Accepted Answer

A)   0.15 m/s
B)   0.24 m/s
C)   0.49 m/s
D)   0.69 m/s
E)   1.46 m/s

Question 14

A rectangular block is moving along a frictionless path when it encounters the circular loop as shown. The block passes points 1,2,3,4,1 before returning to the horizontal track. At point 3:

Accepted Answer

A)   its mechanical energy is a minimum
B)   the forces on it are balanced
C)   it is not accelerating
D)   its speed is a minimum
E)   it experiences a net upward force

Question 15

The potential energy of a 0.20-kg particle moving along the x axis is given by U(x)  = (8.0 J/m2) x2 − (2.0 J/m4) x4. When the particle is at x = 1.0 m the magnitude of its acceleration is:

Accepted Answer

A)   0 m/s2
B)   -8 m/s2
C)   8 m/s2
D)   -40 m/s2
E)   40 m/s2

Question 16

A simple pendulum consists of a 2.0 kg mass attached to a string. It is released from rest at X as shown. Its speed at the lowest point Y is:

Accepted Answer

A)   1.9 m/s
B)   3.7 m/s
C)   4.4 m/s
D)   6.0 m/s
E)   36 m/s

Question 17

A 0.50-kg block attached to an ideal spring with a spring constant of 80 N/m oscillates on a horizontal frictionless surface. When the spring is 4.0 cm longer than its equilibrium length, the speed of the block is 0.50 m/s. The greatest speed of the block is:

Accepted Answer

A)   0.32 m/s
B)   0.55 m/s
C)   0.71 m/s
D)   0.87 m/s
E)   0.93 m/s

Question 18

A block of mass m is initially moving to the right on a horizontal frictionless surface at a speed v. It then compresses a spring of spring constant k. At the instant when the kinetic energy of the block is equal to the potential energy of the spring, the spring is compressed a distance of:

Accepted Answer

A)   2 
C)   (1/4) mv2 
D)   mv2/4k 
E)   (1/4) " class="answers-bank-image d-inline" rel="preload" >
B)   (1/2) mv2
C)   (1/4) mv2
D)   mv2/4k
E)   (1/4)

Question 19

The sum of the kinetic and potential energies of a system of objects is conserved:

Accepted Answer

A)   only when no external force acts on the objects
B)   only when the objects move along closed paths
C)   only when the work done by the resultant external force is zero
D)   always
E)   none of the above

Question 20

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 in a time of 1.4 s. What was the average power expended?

Accepted Answer

A)   0.93 W
B)   4.3 W
C)   5.2 W
D)   8.6 W
E)   10.2 W

Exam 8: Potential Energy and Conservation of Energy

A ball is held at a height H above a floor. It is then released and falls to the floor. If air resistance can be ignored, which of the five graphs below correctly gives the mechanical energy E of the Earth-ball system as a function of the altitude y of the ball?

Correct AnswerverifiedShow Answer

A 0.50-kg block attached to an ideal spring with a spring constant of 80 N/m oscillates on a horizontal frictionless surface. The total mechanical energy is 0.12 J. The greatest speed of the block is:

Correct AnswerverifiedShow Answer

A 700-N man jumps out of a window into a fire net 10 m below. The net stretches 2 m before bringing the man to rest and tossing him back into the air. The maximum potential energy of the net, compared to its unstretched potential energy, is:

Correct AnswerverifiedShow Answer

A 2.2-kg block starts from rest on a rough inclined plane that makes an angle of 25 °\degree° with the horizontal. The coefficient of kinetic friction is 0.25. As the block goes 2.0 m down the plane, the mechanical energy of the Earth-block system changes by:

Correct AnswerverifiedShow Answer

A body at rest in a system is capable of doing work if:

Correct AnswerverifiedShow Answer

A simple pendulum consists of a 2.0 kg mass attached to a string. It is released from rest at X as shown. Its speed at the lowest point Y is:

Correct AnswerverifiedShow Answer

Only if a force on a particle is conservative:

Correct AnswerverifiedShow Answer

A particle moves along the x axis under the influence of a stationary object. The net force on the particle, which is conservative, is given by F = (8N/m3) x3. If the potential energy is taken to be zero for x = 0 then the potential energy is given by:

Correct AnswerverifiedShow Answer

A good example of kinetic energy is provided by:

Correct AnswerverifiedShow Answer

A rectangular block is moving along a frictionless path when it encounters the circular loop as shown. The block passes points 1,2,3,4,1 before returning to the horizontal track. At point 3:

Correct AnswerverifiedShow Answer

A block slides across a rough horizontal table top. The work done by friction changes:

Correct AnswerverifiedShow Answer

A 0.50-kg block attached to an ideal spring with a spring constant of 80 N/m oscillates on a horizontal frictionless surface. When the spring is 4.0 cm longer than its equilibrium length, the speed of the block is 0.50 m/s. The greatest speed of the block is:

Correct AnswerverifiedShow Answer

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 in a time of 1.4 s. What was the average power expended?

Correct AnswerverifiedShow Answer

The sum of the kinetic and potential energies of a system of objects is conserved:

Correct AnswerverifiedShow Answer

The potential energy of a 0.20-kg particle moving along the x axis is given by U(x) =(8.0 J/m2) x2 + (2.0 J/m4) x4. When the particle is at x = 1.0 m it is traveling in the positive x direction with a speed of 5.0 m/s. It next stops momentarily to turn around at x =

Correct AnswerverifiedShow Answer

A 0.50-kg block attached to an ideal spring with a spring constant of 80 N/m oscillates on a horizontal frictionless surface. The total mechanical energy is 0.12 J. The greatest extension of the spring from its equilibrium length is:

Correct AnswerverifiedShow Answer

A block of mass m is initially moving to the right on a horizontal frictionless surface at a speed v. It then compresses a spring of spring constant k. At the instant when the kinetic energy of the block is equal to the potential energy of the spring, the spring is compressed a distance of:

Correct AnswerverifiedShow Answer

A small object of mass m, on the end of a light cord, is held horizontally at a distance r from a fixed support as shown. The object is then released. What is the tension in the cord when the object is at the lowest point of its swing?

Correct AnswerverifiedShow Answer

The potential energy of a 0.20-kg particle moving along the x axis is given by U(x) = (8.0 J/m2) x2 − (2.0 J/m4) x4. When the particle is at x = 1.0 m the magnitude of its acceleration is:

Correct AnswerverifiedShow Answer

Which of the five graphs correctly shows the potential energy of a spring as a function of its elongation x?

Correct AnswerverifiedShow Answer

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Correct Answer
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Correct Answer
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A 2.2-kg block starts from rest on a rough inclined plane that makes an angle of 25 $\degree$ with the horizontal. The coefficient of kinetic friction is 0.25. As the block goes 2.0 m down the plane, the mechanical energy of the Earth-block system changes by:

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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A particle moves along the x axis under the influence of a stationary object. The net force on the particle, which is conservative, is given by F = (8N/m³) x³. If the potential energy is taken to be zero for x = 0 then the potential energy is given by:

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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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The potential energy of a 0.20-kg particle moving along the x axis is given by U(x) =(8.0 J/m²) x²+ (2.0 J/m⁴) x^4. When the particle is at x = 1.0 m it is traveling in the positive x direction with a speed of 5.0 m/s. It next stops momentarily to turn around at x =

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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The potential energy of a 0.20-kg particle moving along the x axis is given by U(x) = (8.0 J/m²) x²− (2.0 J/m⁴) x⁴. When the particle is at x = 1.0 m the magnitude of its acceleration is:

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Correct Answer
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