Question 1

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)   10 N
B)   20 N
C)   30 N
D)   40 N
E)   50 NF) B) and C)
G) C) and E)

Question 2

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 .lb
B)   1 J
C)   10 J
D)   0.1 J
E)   zeroF) B) and C)
G) C) and D)

Question 3

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 cmF) All of the above
G) A) and E)

Question 4

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 greatF) A) and B)
G) D) and E)

Question 5

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 WF) A) and B)
G) D) and E)

Question 6

A man moves the 10-g object shown in a vertical plane from position X to position Y along a circular track of radius 20 m. The process takes 0.75 min. The work done by the man is about:

Accepted Answer

A)   1 J
B)   2 J
C)   4 J
D)   6 J
E)   12 JF) None of the above
G) B) and C)

Question 7

A particle starts from rest and is acted on by a net force that does work at a rate that is proportional to the time t. The speed of the particle is proportional to:

Accepted Answer

A)   2 
D)     
E)   1/t" class="answers-bank-image d-inline" rel="preload" >
B)   t
C)   t2
D)   2 
D)     
E)   1/t" class="answers-bank-image d-inline" rel="preload" >
E)   1/tF) C) and D)
G) A) and E)

Exam 7: Kinetic Energy and Work

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:

Correct Answer
verified

A man moves the 10-g object shown in a vertical plane from position X to position Y along a circular track of radius 20 m. The process takes 0.75 min. The work done by the man is about:

Correct Answer
verified

A particle starts from rest and is acted on by a net force that does work at a rate that is proportional to the time t. The speed of the particle is proportional to:

Correct Answer
verified

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:

Correct Answer
verified

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

Correct Answer
verified

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:

Correct Answer
verified

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:

Correct Answer
verified

Exam 7: Kinetic Energy and Work

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:

Correct AnswerverifiedShow Answer

A man moves the 10-g object shown in a vertical plane from position X to position Y along a circular track of radius 20 m. The process takes 0.75 min. The work done by the man is about:

Correct AnswerverifiedShow Answer

A particle starts from rest and is acted on by a net force that does work at a rate that is proportional to the time t. The speed of the particle is proportional to:

Correct AnswerverifiedShow Answer

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:

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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:

Correct AnswerverifiedShow Answer

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:

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

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:

Correct Answer
verified