Question 1

In the plot shown of force vs.distance, approximately how much work is done in moving an object from x = 5 m to x = 15 m?

Accepted Answer

A) 10 J 
B) 55 J 
C) 125 J 
D) 275 J 
E) cannot be calculated without knowing the mass of the object 
A) 10 J 
B) 55 J 
C) 125 J 
D) 275 J 
E) cannot be calculated without knowing the mass of the object

Question 2

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 
A) 2.5 W 
B) 25 W 
C) 75 W 
D) 100 W 
E) 500 W

Question 3

A watt .second is a unit of:

Accepted Answer

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

Question 4

Which of the following is NOT a correct unit for work?

Accepted Answer

A) erg 
B) ft.lb 
C) watt 
D) newton.meter 
E) joule 
A) erg 
B) ft.lb 
C) watt 
D) newton.meter 
E) joule

Question 5

An ideal spring, with a pointer attached to its end, hangs next to a scale.With a 100-N weight attached, the pointer indicates "40" on the scale as shown.Using a 200-N weight instead results in "60" on the scale.Using an unknown weight X instead results in "30" on the scale.The weight of X is:

Accepted Answer

A) 20 N 
B) 30 N 
C) 40 N 
D) 50 N 
E) 75 N 
A) 20 N 
B) 30 N 
C) 40 N 
D) 50 N 
E) 75 N

Question 6

A 1.5 kg crate falls from a height of 2.0 m onto an industrial spring scale with a spring constant of 1.5*105 N/m.At its greatest compression the reading on the scale is:

Accepted Answer

A) 15 N 
B) 29 N 
C) 1.5 * 103 N 
D) 2.1 * 103 N 
E) 3.0 * 103 N 
A) 15 N 
B) 29 N 
C) 1.5 * 103 N 
D) 2.1 * 103 N 
E) 3.0 * 103 N

Question 7

Two objects with masses, m1 and m2, have the same kinetic energy and are both moving to the right.The same constant force is applied to the left to both masses.If m1 = 4m2, the ratio of the stopping distance of m1 to that of m2 is:

Accepted Answer

A) 1:4 
B) 4:1 
C) 1:2 
D) 2:1 
E) 1:1 
A) 1:4 
B) 4:1 
C) 1:2 
D) 2:1 
E) 1:1

Question 8

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

Question 9

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. 
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 10

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

Question 11

The velocity of a particle moving along the x axis changes from vi to vf.For which values of vi and vf is the total work done on the particle positive?

Accepted Answer

A) vi = 5m/s, vf = 2m/s 
B) vi = 5m/s, vf = -2m/s 
C) vi = -5m/s, vf = -2m/s 
D) vi = -5m/s, vf = 2m/s 
E) vi = -2m/s, vf = -5m/s 
A) vi = 5m/s, vf = 2m/s 
B) vi = 5m/s, vf = -2m/s 
C) vi = -5m/s, vf = -2m/s 
D) vi = -5m/s, vf = 2m/s 
E) vi = -2m/s, vf = -5m/s

Question 12

Power has the dimensions of:

Accepted Answer

A) ML2/T2 
B) MT/L2 
C) ML/T2 
D) ML2/T3 
E) none of these 
A) ML2/T2 
B) MT/L2 
C) ML/T2 
D) ML2/T3 
E) none of these

Question 13

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

Question 14

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 
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

Question 15

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

Question 16

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) 0 J 
B) 2.5 * 105 J 
C) 5.0 * 105 J 
D) 2.5 *106 J 
E) 5.0 *106 J 
A) 0 J 
B) 2.5 * 105 J 
C) 5.0 * 105 J 
D) 2.5 *106 J 
E) 5.0 *106 J

Question 17

A 5.0-kg cart is moving horizontally at 6.0 m/s.In order to change its speed to 10.0 m/s, the net work done on the cart must be:

Accepted Answer

A) 20 J 
B) 40 J 
C) 90 J 
D) 160 J 
E) 400 J 
A) 20 J 
B) 40 J 
C) 90 J 
D) 160 J 
E) 400 J

Question 18

A 1-kg block is lifted vertically 1 m at constant speed by a boy.The work done by the boy is about:

Accepted Answer

A) 1 ft .0lb 
B) 1 J 
C) 10 J 
D) 0.1 J 
E) 0 J 
A) 1 ft .0lb 
B) 1 J 
C) 10 J 
D) 0.1 J 
E) 0 J

Question 19

In raising an object to a given height by means of an inclined plane, as compared with raising the object vertically, there is a reduction in:

Accepted Answer

A) work required 
B) distance pushed 
C) friction 
D) force required 
E) value of the acceleration due to gravity 
A) work required 
B) distance pushed 
C) friction 
D) force required 
E) value of the acceleration due to gravity

Question 20

A 0.50-kg object moves in a horizontal circular track with a radius of 2.5 m.An external force of 3.0 N, always tangent to the track, causes the object to speed up as it goes around.If it starts from rest its speed at the end of one revolution is:

Accepted Answer

A) 5.5 m/s 
B) 14 m/s 
C) 15 m/s 
D) 18 m/s 
E) 21 m/s 
A) 5.5 m/s 
B) 14 m/s 
C) 15 m/s 
D) 18 m/s 
E) 21 m/s

Exam 7: Kinetic Energy and Work

In the plot shown of force vs.distance, approximately how much work is done in moving an object from x = 5 m to x = 15 m?

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:

A watt .second is a unit of:

Which of the following is NOT a correct unit for work?

An ideal spring, with a pointer attached to its end, hangs next to a scale.With a 100-N weight attached, the pointer indicates "40" on the scale as shown.Using a 200-N weight instead results in "60" on the scale.Using an unknown weight X instead results in "30" on the scale.The weight of X is:

A 1.5 kg crate falls from a height of 2.0 m onto an industrial spring scale with a spring constant of 1.5*105 N/m.At its greatest compression the reading on the scale is:

Two objects with masses, m1 and m2, have the same kinetic energy and are both moving to the right.The same constant force is applied to the left to both masses.If m1 = 4m2, the ratio of the stopping distance of m1 to that of m2 is:

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:

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

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

The velocity of a particle moving along the x axis changes from vi to vf.For which values of vi and vf is the total work done on the particle positive?

Power has the dimensions of:

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

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 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?

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?

A 5.0-kg cart is moving horizontally at 6.0 m/s.In order to change its speed to 10.0 m/s, the net work done on the cart must be:

A 1-kg block is lifted vertically 1 m at constant speed by a boy.The work done by the boy is about:

In raising an object to a given height by means of an inclined plane, as compared with raising the object vertically, there is a reduction in:

A 0.50-kg object moves in a horizontal circular track with a radius of 2.5 m.An external force of 3.0 N, always tangent to the track, causes the object to speed up as it goes around.If it starts from rest its speed at the end of one revolution is:

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A 1.5 kg crate falls from a height of 2.0 m onto an industrial spring scale with a spring constant of 1.5*10⁵ N/m.At its greatest compression the reading on the scale is:

Two objects with masses, m₁ and m₂, have the same kinetic energy and are both moving to the right.The same constant force is applied to the left to both masses.If m₁ = 4m₂, the ratio of the stopping distance of m₁ to that of m₂ is:

The velocity of a particle moving along the x axis changes from v_i to v_f.For which values of v_i and v_f is the total work done on the particle positive?