Question 1

Which of the following bodies has the largest kinetic energy?

Accepted Answer

A)  Mass 3M and speed V 
B)  Mass 3M and speed 2V 
C)  Mass 2M and speed 3V 
D)  Mass M and speed 4V 
E)  All four of the above have the same kinetic energy

Question 2

A particle moving along the x axis is acted upon by a single force F = F0e-kx, where F0 and k are constants. The particle is released from rest at x = 0. It will attain a maximum kinetic energy of:

Accepted Answer

A)  F0/k 
B)  F0/ek 
C)  kF0 
D)  1/2(kF0)2 
E)  kekF0

Question 3

At time t = 0 a particle starts moving along the x axis. If its kinetic energy increases uniformly with t the net force acting on it must be:

Accepted Answer

A)  constant 
B)  proportional to t 
C)  inversely proportional to t 
D)   
E)

Question 4

When a certain rubber band is stretched a distance x, it exerts a restoring force of magnitude F = Ax, where A is a constant. The work done by a person in stretching this rubber band from x = 0 to x = L is:

Accepted Answer

A)  AL2 
B)  A + 2L 
C)  A + 2L2 
D)  A/L 
E)  AL2/2

Question 5

A particle moves 5 m in the positive x direction while being acted upon by a constant force  The work done on the particle by this force is:

Accepted Answer

A)  20 J 
B)  10 J 
C)  -20 J 
D)  30 J 
E)  is impossible to calculate without knowing other forces

Question 6

The amount of work required to stop a moving object is equal to the:

Accepted Answer

A)  velocity of the object 
B)  kinetic energy of the object 
C)  mass of the object times its acceleration 
D)  mass of the object times its velocity 
E)  square of the velocity of the object

Question 7

A watt .second is a unit of:

Accepted Answer

A)  force 
B)  power 
C)  displacement 
D)  speed 
E)  energy

Question 8

An ideal spring is hung vertically from the ceiling. When a 2.0-kg mass hangs at rest from it the spring is extended 6.0 cm from its relaxed length. A downward external force is now applied to the mass to extend the spring an additional 10 cm. While the spring is being extended by the force, the work done by the spring is:

Accepted Answer

A)  -3.6 J 
B)  -3.3 J 
C)  -3.4 *10-5 J 
D)  3.3 J 
E)  3.6 J

Question 9

A sledge (including load) weighs 5000 N. It is pulled on level snow by a dog team exerting a horizontal force on it. The coefficient of kinetic friction between sledge and snow is 0.05. How much work is done by the dog team pulling the sledge 1000 m at constant speed?

Accepted Answer

A)  2.5 * 104 J 
B)  2.5 * 105 J 
C)  5.0 * 105 J 
D)  2.5*106 J 
E)  5.0* 106 J

Question 10

An 8-N block slides down an incline. It has an initial speed of 7 m/s. The work done by the resultant force on this block is:

Accepted Answer

A)  3 J 
B)  6 J 
C)  56 J 
D)  impossible to calculate without more information 
E)  none of these

Question 11

A man pushes an 80-N crate a distance of 5.0 m upward along a frictionless slope that makes an angle of 30 ° with the horizontal. His force is parallel to the slope. If the speed of the crate decreases at a rate of 1.5 m/s2, then the work done by the mand is:

Accepted Answer

A)  -200 J 
B)  61 J 
C)  140 J 
D)  200 J 
E)  260 J

Question 12

A man pushes an 80-N crate a distance of 5.0 m upward along a frictionless slope that makes an angle of 30 °  with the horizontal. The force he exerts is parallel to the slope. If the speed of the crate is constant, then the work done by the man is:

Accepted Answer

A)  -200 J 
B)  61 J 
C)  140 J 
D)  200 J 
E)  260 J

Question 13

Which of the following groups does NOT contain a scalar quantity?

Accepted Answer

A)  velocity, force, power 
B)  displacement, acceleration, force 
C)  acceleration, speed, work 
D)  energy, work, distance 
E)  pressure, weight, time

Question 14

A person holds a 80-N weight 2 m above the floor for 30 seconds. The power required to do this is:

Accepted Answer

A)  80 W 
B)  40 W 
C)  20 W 
D)  10 W 
E)  none of these

Question 15

Which of the following five quantities is NOT an expression for energy? Here m is a mass, g is the acceleration due to gravity, h and d are distances, F is a force, v is a speed, a is an acceleration, P is power, and t is time.

Accepted Answer

A)  mgh 
B)  Fd 
C)  1/2mv2 
D)  ma 
E)  Pt

Question 16

When a certain rubber band is stretched a distance x, it exerts a restoring force F = ax + bx2, where a and b are constants. The work done in stretching this rubber band from x = 0 to x = L is:

Accepted Answer

A)  aL2 + bLx3 
B)  aL + 2bL2 
C)  a + 2bL 
D)  bL 
E)  aL2/2 + bL3/3

Question 17

A 4-kg cart starts up an incline with a speed of 3 m/s and comes to rest 2 m up the incline. The total work done on the cart is:

Accepted Answer

A)  6 J 
B)  8 J 
C)  12 J 
D)  18 J 
E)  impossible to calculate without more information

Question 18

Three identical springs (X,Y,Z) are arranged as shown. When a 4.0-kg mass is hung on X, the mass descends 3.0 cm. When a 6.0-kg mass is hung on Y, the mass descends:

Accepted Answer

A)  2.0 cm 
B)  4.0 cm 
C)  4.5 cm 
D)  6.0 cm 
E)  9.0 cm

Question 19

The weight of an object on the moon is one-sixth of its weight on the Earth. The ratio of the kinetic energy of a body on the Earth moving with speed V to that of the same body moving with speed V on the moon is:

Accepted Answer

A)  6:1 
B)  36:1 
C)  1:1 
D)  1:6 
E)  1:36

Question 20

A 50-N force on is the only force a 2-kg crate that starts from rest. At the instant the object has gone 2 m the rate at which the force is doing work is:

Accepted Answer

A)  2.5 W 
B)  25 W 
C)  75 W 
D)  100 W 
E)  1000 W

Exam 7: Kinetic Energy and Work