21. Which of the following statements is true about power?
a) Power is the rate at which work is done
b) Power is equal to force times velocity
c) Power is a scalar quantity
d) Power is measured in joules
22. Which of the following statements is true about mechanical advantage?
a) It is the ratio of output force to input force
b) It is the ratio of input force to output force
c) It is always greater than 1
d) It is always less than 1
23. Which of the following statements is true about efficiency?
a) It is the ratio of useful work output to total work input
b) It is the ratio of total work input to useful work output
c) It is always greater than 1
d) It is always less than 1
24. Which of the following statements is true about simple machines?
a) They can increase the amount of work done on an object
b) They can increase the distance over which a force is applied
c) They can change the direction of a force
d) All of the above
25. Which of the following is an example of a first-class lever?
a) A seesaw
b) A wheelbarrow
c) Pliers
d) A hammer
