You are doing exercises at the gym. When you lift a weight over your head, you push upward on it both as you lift it and as you lower it. However, when you work out with a particular exercise machine, you push upward as you lift its bar but must pull downward to lower that bar. When you use that exercise machine,
A)	you do work on the bar as you raise it and as you lower it.
B)	you do work on the bar as you raise it but it does work on you as you lower it.
C)	its bar does work on you as you raise it and as you lower it.
D)	its bar does work on you as you raise it but you do work on it as you lower it.
Answer:A
You are doing exercises at the gym. When you lift a weight over your head, you push upward on it both as you lift it and as you lower it. However, when you work out with a particular exercise machine, you push upward as you lift its bar but must pull downward to lower that bar. When you use that exercise machine,
A)	you do work on the bar as you raise it and as you lower it. B)	you do work on the bar as you raise it but it does work on you as you lower it. C)	its bar does work on you as you raise it and as you lower it. D)	its bar does work on you as you raise it but you do work on it as you lower it.