Question 1

A nonconservative force:

Accepted Answer

A) violates Newton's second law 
B) violates Newton's third law 
C) cannot do any work 
D) must be perpendicular to the velocity of the particle on which it acts 
E) none of the above 
A) violates Newton's second law 
B) violates Newton's third law 
C) cannot do any work 
D) must be perpendicular to the velocity of the particle on which it acts 
E) none of the above

Question 2

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

Question 3

A force on a particle is conservative if:

Accepted Answer

A) its work equals the change in the kinetic energy of the particle 
B) it obeys Newton's second law 
C) it obeys Newton's third law 
D) its work depends on the end points of the motion, not this the path between 
E) it is not a frictional force 
A) its work equals the change in the kinetic energy of the particle 
B) it obeys Newton's second law 
C) it obeys Newton's third law 
D) its work depends on the end points of the motion, not this the path between 
E) it is not a frictional force

Question 4

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 5

Two objects interact with each other and with no other objects.Initially object A has a speed of 5 m/s and object B has a speed of 10 m/s.In the course of their motion they return to their initial positions.Then A has a speed of 4 m/s and B has a speed of 7 m/s.We can conclude:

Accepted Answer

A) the potential energy changed from the beginning to the end of the trip 
B) mechanical energy was increased by nonconservative forces 
C) mechanical energy was decreased by nonconservative forces 
D) mechanical energy was increased by conservative forces 
E) mechanical energy was decreased by conservative forces 
A) the potential energy changed from the beginning to the end of the trip 
B) mechanical energy was increased by nonconservative forces 
C) mechanical energy was decreased by nonconservative forces 
D) mechanical energy was increased by conservative forces 
E) mechanical energy was decreased by conservative forces

Question 6

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 7

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 8

Which one of the following five quantities CANNOT be used as a unit of potential energy?

Accepted Answer

A) watt.second 
B) gram.cm/s2 
C) joule 
D) kg.m2/s2 
E) ft.lb 
A) watt.second 
B) gram.cm/s2 
C) joule 
D) kg.m2/s2 
E) ft.lb

Question 9

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

Question 10

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 
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 11

The wound spring of a clock possesses:

Accepted Answer

A) kinetic but no potential energy 
B) potential but no kinetic energy 
C) both potential and kinetic energy in equal amounts 
D) neither potential nor kinetic energy 
E) both potential and kinetic energy, but more kinetic energy than potential energy 
A) kinetic but no potential energy 
B) potential but no kinetic energy 
C) both potential and kinetic energy in equal amounts 
D) neither potential nor kinetic energy 
E) both potential and kinetic energy, but more kinetic energy than potential energy

Question 12

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

Question 13

No kinetic energy is possessed by:

Accepted Answer

A) a shooting star 
B) a rotating propeller on a moving airplane 
C) a pendulum at the bottom of its swing 
D) an elevator standing at the fifth floor 
E) a cyclone 
A) a shooting star 
B) a rotating propeller on a moving airplane 
C) a pendulum at the bottom of its swing 
D) an elevator standing at the fifth floor 
E) a cyclone

Question 14

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

Question 15

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 16

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

Question 17

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

Question 18

Given a potential energy function U(x), the corresponding force is in the positive x direction if:

Accepted Answer

A) U is positive 
B) U is negative 
C) U is an increasing function of x 
D) U is a decreasing function of x 
E) it is impossible to obtain the direction of from U 
A) U is positive 
B) U is negative 
C) U is an increasing function of x 
D) U is a decreasing function of x 
E) it is impossible to obtain the direction of from U

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 
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

The potential energy of a body of mass m is given by U = -mgx + 1/2kx2.The corresponding force is:

Accepted Answer

A) -mgx2/2 + kx3/6 
B) mgx2/2 - kx3/6 
C) -mg + kx/2 
D) -mg + kx 
E) mg - kx 
A) -mgx2/2 + kx3/6 
B) mgx2/2 - kx3/6 
C) -mg + kx/2 
D) -mg + kx 
E) mg - kx

Exam 8: Potential Energy and Conservation of Energy

A nonconservative force:

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:

A force on a particle is conservative if:

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:

Two objects interact with each other and with no other objects.Initially object A has a speed of 5 m/s and object B has a speed of 10 m/s.In the course of their motion they return to their initial positions.Then A has a speed of 4 m/s and B has a speed of 7 m/s.We can conclude:

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:

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?

Which one of the following five quantities CANNOT be used as a unit of potential energy?

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:

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

The wound spring of a clock possesses:

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

No kinetic energy is possessed by:

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:

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.

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

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?

Given a potential energy function U(x), the corresponding force is in the positive x direction if:

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

The potential energy of a body of mass m is given by U = -mgx + 1/2kx2.The corresponding force is:

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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:

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:

The potential energy of a body of mass m is given by U = -mgx + 1/2kx².The corresponding force is: