Question 1

This plot shows an object being moved by a series of forces. Which segments of the motion could have been caused by fixed springs?

Accepted Answer

A)  None of the segments could represent work being done by springs. 
B)  Any of the segments could represent work being done by springs. 
C)  Segments A and C only. 
D)  Segments B and D only. 
E)  Segment A only.

Question 2

A man pushes an 80-N crate a distance of 5.0 m upward along a frictionless slope that makes an angle of 30 $\degree$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 man is:

Accepted Answer

A)  -200 J 
B)  61 J 
C)  140 J 
D)  200 J 
E)  400 J

Question 3

A watt per hour is a unit of:

Accepted Answer

A)  energy 
B)  power 
C)  force 
D)  acceleration 
E)  none of these

Question 4

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 5

One watt is:

Accepted Answer

A)  1 kg. m/s3 
B)  1 kg . m2/s 
C)  1 kg. m2/s3 
D)  1 kg. m/s 
E)  1 kg . m2/s2

Question 6

A block is attached to the end of an ideal spring and moved from coordinate xi to coordinate xf. The relaxed position is at x = 0. The work done by spring is positive if:

Accepted Answer

A)  xi = 2 cm and xf = 4 cm 
B)  xi = -2 cm and xf = 4 cm 
C)  xi = -2 cm and xf = -4 cm 
D)  xi = 2 cm and xf = -4 cm 
E)  xi = -4 cm and xf = -2 cm

Question 7

A woman lifts a barbell 2.0 m in 5.0 s. If she lifts it the same distance in 10 s, the work done by her is:

Accepted Answer

A)  four times as great 
B)  two times as great 
C)  the same 
D)  half as great 
E)  one-fourth as great

Question 8

Camping equipment weighing 6000 N is pulled across a frozen lake by means of a horizontal rope. The coefficient of kinetic friction is 0.05. The work done by the campers in pulling the equipment 1000 m at constant velocity is:

Accepted Answer

A)  0 J 
B)  1.5 *105 J 
C)  3.0 * 105 J 
D)  2.9 * 106 J 
E)  6.0* 106 J

Question 9

A man pulls a 100-N crate up a frictionless 30 $\degree$slope 5 m high as shown. Assuming that the crate moves at constant speed, the work done by the man is:

Accepted Answer

A)  -500 J 
B)  -250 J 
C)  0 J 
D)  250 J 
E)  500 J

Question 10

A 50-N force is the only force on a 2-kg crate that starts from rest. At the instant the crate 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)  500 W

Question 11

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

Question 12

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

Accepted Answer

A)  5.3 W 
B)  40 W 
C)  80 W 
D)  160 W 
E)  none of these

Question 13

A 50-N force acts on a 2-kg crate that starts from rest. When the force has been acting for 2 s the rate at which it is doing work is:

Accepted Answer

A)  100 W 
B)  1000 W 
C)  2500 W 
D)  5000 W 
E)  63000 W

Question 14

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

Accepted Answer

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

Question 15

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)  20 J 
B)  28 J 
C)  56 J 
D)  impossible to calculate without more information 
E)  none of these

Question 16

A 2-kg object is moving at 3 m/s. A 4-N force is applied in the direction of motion and then removed after the object has traveled an additional 5 m. The work done by this force is:

Accepted Answer

A)  9 J 
B)  18 J 
C)  20 J 
D)  29 J 
E)  38 J

Question 17

A man pulls a sled along a rough horizontal surface by applying a constant force at an angle $\theta$ above the horizontal. In pulling the sled a horizontal distance d, the work done by the man is:

Accepted Answer

A)  Fd 
B)  Fd cos $\theta$ 
C)  Fd sin $\theta$ 
D)  Fd/cos$\theta$ 
E)  Fd/sin $\theta$

Question 18

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 19

A mass of 47 kg is moving horizontally as a force of 190 N, directed at 25° below the horizontal, is exerted on it. When its speed is 7.3 m/s, what is the rate at which the force is doing work?

Accepted Answer

A)  0 W 
B)  340 W 
C)  590 W 
D)  1300 W 
E)  1400 W

Question 20

An 8000-N car is traveling at 12 m/s along a horizontal road when the brakes are applied. The car skids to a stop in 4.0 s. How much kinetic energy does the car lose in this time?

Accepted Answer

A)  4.8 * 104 J 
B)  5.9 * 104 J 
C)  1.2 *105 J 
D)  5.8 *105 J 
E)  4.8 * 106 J

Exam 7: Kinetic Energy and Work

This plot shows an object being moved by a series of forces. Which segments of the motion could have been caused by fixed springs?

A man pushes an 80-N crate a distance of 5.0 m upward along a frictionless slope that makes an angle of 30 $\degree$ 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 man is:

A watt per hour is a unit of:

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.

One watt is:

A block is attached to the end of an ideal spring and moved from coordinate x_i to coordinate x_f. The relaxed position is at x = 0. The work done by spring is positive if:

A woman lifts a barbell 2.0 m in 5.0 s. If she lifts it the same distance in 10 s, the work done by her is:

Camping equipment weighing 6000 N is pulled across a frozen lake by means of a horizontal rope. The coefficient of kinetic friction is 0.05. The work done by the campers in pulling the equipment 1000 m at constant velocity is:

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

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:

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

A 50-N force acts on a 2-kg crate that starts from rest. When the force has been acting for 2 s the rate at which it is doing work is:

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

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:

A 2-kg object is moving at 3 m/s. A 4-N force is applied in the direction of motion and then removed after the object has traveled an additional 5 m. The work done by this force is:

A man pulls a sled along a rough horizontal surface by applying a constant force at an angle $\theta$ above the horizontal. In pulling the sled a horizontal distance d, the work done by the man is:

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:

A mass of 47 kg is moving horizontally as a force of 190 N, directed at 25° below the horizontal, is exerted on it. When its speed is 7.3 m/s, what is the rate at which the force is doing work?

An 8000-N car is traveling at 12 m/s along a horizontal road when the brakes are applied. The car skids to a stop in 4.0 s. How much kinetic energy does the car lose in this time?

Exam 7: Kinetic Energy and Work

This plot shows an object being moved by a series of forces. Which segments of the motion could have been caused by fixed springs?

A man pushes an 80-N crate a distance of 5.0 m upward along a frictionless slope that makes an angle of 30 °\degree° 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 man is:

A watt per hour is a unit of:

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.

One watt is:

A block is attached to the end of an ideal spring and moved from coordinate xi to coordinate xf. The relaxed position is at x = 0. The work done by spring is positive if:

A woman lifts a barbell 2.0 m in 5.0 s. If she lifts it the same distance in 10 s, the work done by her is:

Camping equipment weighing 6000 N is pulled across a frozen lake by means of a horizontal rope. The coefficient of kinetic friction is 0.05. The work done by the campers in pulling the equipment 1000 m at constant velocity is:

A man pulls a 100-N crate up a frictionless 30 °\degree° slope 5 m high as shown. Assuming that the crate moves at constant speed, the work done by the man is:

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

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:

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

A 50-N force acts on a 2-kg crate that starts from rest. When the force has been acting for 2 s the rate at which it is doing work is:

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

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:

A 2-kg object is moving at 3 m/s. A 4-N force is applied in the direction of motion and then removed after the object has traveled an additional 5 m. The work done by this force is:

A man pulls a sled along a rough horizontal surface by applying a constant force at an angle θ\thetaθ above the horizontal. In pulling the sled a horizontal distance d, the work done by the man is:

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:

A mass of 47 kg is moving horizontally as a force of 190 N, directed at 25° below the horizontal, is exerted on it. When its speed is 7.3 m/s, what is the rate at which the force is doing work?

An 8000-N car is traveling at 12 m/s along a horizontal road when the brakes are applied. The car skids to a stop in 4.0 s. How much kinetic energy does the car lose in this time?

A man pushes an 80-N crate a distance of 5.0 m upward along a frictionless slope that makes an angle of 30 $\degree$ 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 man is:

A block is attached to the end of an ideal spring and moved from coordinate x_i to coordinate x_f. The relaxed position is at x = 0. The work done by spring is positive if:

A man pulls a sled along a rough horizontal surface by applying a constant force at an angle $\theta$ above the horizontal. In pulling the sled a horizontal distance d, the work done by the man is: