22 Questions

22 question on energy and work; most are conceptual

Questions and Answers

- 1.A car drives off a cliff going 25 m/s. How fast is it going after falling 10 meters downward?
- A.
20.71 m/s

- B.
26.93 m/s

- C.
28.65 m/s

- D.
35.00 m/s

- 2.
**An apple falls from a tree limb. In falling 3.5 meters, it loses 6.5 J in gravitational potential energy. How****much kinetic energy does it gain?(Include units in your answer.)** - 3.A man does 30 J of work on a box. At the same time, friction does -20 J of work. No other force does work. How much does the kinetic energy of the box change?(Include units in your answer.)
- 4.A man lifts a 28.0 N book by pushing upward with a force of 28.0 N. He lifts the book 0.85 meters. How much work does the man do on the book?(Include units in your answer. State your answer to the tenths place.)
- 5.A man pushes on a 5.0 kg block (initially at rest) with a force of 12 N over a distance of 0.25 meters. If the force is in the direction of motion, and if there are no other forces doing work, then what speed does the block acquire?(Answer in the format: #.# m/s )
- 6.How much work is required to increase the kinetic energy of a 500-kg motorcycle by 400 J?(Include units in your answer.)
- 7.A book has a mass of 6.0 kg. If you push upward on it with a force of 70 N, then...
- A.
It speeds up moving up

- B.
It slows down moving up

- C.
It rises at a constant speed

- D.
It does not move

- 8.Kinetic energy can be negative.
- A.
True

- B.
False

- 9.A 2000-kg car doubles its speed. Its kinetic energy...
- A.
Shrinks to 1/2 its original value

- B.
Does not change

- C.
Doubles

- D.
Quadruples

- 10.A woman does 60 J of work on a large box. At the same time, friction does -20 J of work on it, and gravity does -15 J of work on it. How much does the mechanical energy of the box change?(Include units in your answer.)
- 11.A woman does 60 J of work on a large box. At the same time, friction does -20 J of work on it, and gravity does -15 J of work on it. How much does the kinetic energy of the box change?(Include units in your answer.)
- 12.A woman does 60 J of work on a large box. At the same time, friction does -20 J of work on it, and gravity does -15 J of work on it. How much does the potential energy of the box change?(Include units in your answer.)
- 13.A sled is sliding down a rough hill. Gravity does 80 J of work on it, while friction does -20 J of work on it. How much does the mechanical energy of the sled change?(Include units in your answer. A reduction in energy should be entered as a negative number.)
- 14.A sled is sliding down a rough hill. Gravity does 80 J of work on it, while friction does -20 J of work on it. If the sled began from rest, and it has a mass of 20 kg, then what is its final speed after the work is done?(Answer in the format: #.# m/s)
- 15.A 100-kg roller coaster car moves along a frictionless track. At a low point on the track, the car is moving at 35 m/s. The car can travel no higher than ________ meters above this point.(Don't include units. Answer to the tenths place.)
- 16.A man is walking forward at a constant speed, carrying a jar of pennies. The height of the jar does not change. If the man walks forward 10 meters, how much work has he done on the jar?
- A.
No work

- B.
Some positive amount of work but we need more information to find it

- C.
Some negative amount of work but we need more information to find it

- 17.Is it possible for gravity to do negative work on some object but the TOTAL work on the object is zero?
- A.
Yes

- B.
No

- 18.A 30 N force, in some object's direction of motion, causes the object to gain 90 J of kinetic energy. Over what distance does the force act? (Assume no other forces are doing work.)(Include units in your answer.)
- 19.The total work done on some object is 100 J. If gravity does 40 J of work, how much work must be done by an external force or forces?(Include units in your answer.)
- 20.It is possible for a person to do negative work on an object.
- A.
True

- B.
False

- 21.If a car has 12,000,000 J of kinetic energy, and friction does -8,000,000 J of work on it, then how much kinetic energy will the car have left? (Assume no other force does work.)(Do NOT include commas in your answer. But DO include units.)
- 22.A book is shoved across a level table, but friction quickly brings it to rest. There is a decrease in the book's kinetic energy. Where did this energy go?
- A.
It went into gravitational potential energy

- B.
It was turned into thermal energy now contained in the book (but NOT the table)

- C.
It was turned into thermal energy now contained in the table (but NOT the book)

- D.
It was turned in thermal energy, some of which went to the book and some of which went to the table