16. What is the work done by gravity when an object is lifted vertically?
a) Positive
b) Negative
c) Zero
d) Cannot be determined
Answer: a) Positive
17. A ball is thrown upwards. What happens to its potential energy?
a) It increases
b) It decreases
c) It remains constant
d) It cannot be determined
Answer: a) It increases
18. A person pushes a block horizontally. If the force and displacement are perpendicular to each other, what is the work done on the block?
a) Positive
b) Negative
c) Zero
d) Cannot be determined
Answer: c) Zero
19. A machine does 500 J of work in 5 seconds. What is its power?
a) 100 W
b) 250 W
c) 500 W
d) 1000 W
Answer: b) 250 W
20. Which of the following is an example of kinetic energy?
a) A stretched rubber band
b) A battery
c) A moving car
d) A compressed spring
Answer: c) A moving car
