Question 1

A line drive to the shortstop is caught at the same height as it was originally hit.Over its entire flight the work done by gravity and the work done by air resistance, respectively, are:

Accepted Answer

A) zero; positive 
B) zero; negative 
C) positive; negative 
D) negative; positive 
E) negative; negative

Question 2

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

Question 3

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 4

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 5

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

Question 6

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.An upward external force is then applied to the block to move it upward a distance of 16 cm.While the block is being raised by the force, the work done by the spring is

Accepted Answer

A) -1.0 J 
B) -0.52 J 
C) -0.26 J 
D) 0.52 J 
E) 1.0 J

Question 7

A 2-kg block is attached to a horizontal ideal spring with a spring constant of 200 N/m.When the spring has its equilibrium length the block is given a speed of 5 m/s.What is the maximum elongation of the spring?

Accepted Answer

A) 0 m 
B) 0.5 m 
C) 5 m 
D) 10 m 
E) 100 m

Question 8

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 man is:

Accepted Answer

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

Question 9

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.The work done by the external force as the mass makes one revolution is:

Accepted Answer

A) 7.5 J 
B) 24 J 
C) 47 J 
D) 94 J 
E) 120 J

Question 10

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 11

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 12

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 13

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 14

A particle moves 5 m in the positive x direction while being acted upon by a constant force  = (4 N)  + (2 N  )- (4 N)  .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 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

Question 16

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

Question 17

An escalator is used to move 20 people (60 kg each)per minute from the first floor of a department store to the second floor, 5 m above.The power required is approximately:

Accepted Answer

A) 100 W 
B) 200 W 
C) 1000 W 
D) 2000 W 
E) 60,000 W

Question 18

Power has the dimensions of:

Accepted Answer

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

Question 19

A force  = (4.1 N)  + (2.6 N  )- (4.7 N)  acts on a mass of 2.3 kg as it moves in the x direction at a speed of 7.2 m/s.What is the rate at which the force is doing work?

Accepted Answer

A) 8.8 W 
B) 16 W 
C) 30 W 
D) 49 W 
E) 60 W

Question 20

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

Exam 7: Kinetic Energy and Work

A line drive to the shortstop is caught at the same height as it was originally hit.Over its entire flight the work done by gravity and the work done by air resistance, respectively, are:

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

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:

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

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?

A 2-kg block is attached to a horizontal ideal spring with a spring constant of 200 N/m.When the spring has its equilibrium length the block is given a speed of 5 m/s.What is the maximum elongation of the spring?

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 man is:

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.The work done by the external force as the mass makes one revolution is:

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

One watt is:

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:

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.

A particle moves 5 m in the positive x direction while being acted upon by a constant force = (4 N) + (2 N ) - (4 N) .The work done on the particle by this force 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 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:

An escalator is used to move 20 people (60 kg each) per minute from the first floor of a department store to the second floor, 5 m above.The power required is approximately:

Power has the dimensions of:

A force = (4.1 N) + (2.6 N ) - (4.7 N) acts on a mass of 2.3 kg as it moves in the x direction at a speed of 7.2 m/s.What is the rate at which the force is doing work?

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: