Question

(A bodybuilder loads a bar with 550 Newton's (-125 pounds)of weight and pushes the bar over her head 10 times. Each time he lifts the weight 0.5 meters. How much work (J) does she do?) If she pushes the bar 10 times in 20 seconds, how much power did she use?

Answer 1

Work = (force) x (distance)

Each time she lifts the weight, she does: (550 N) x (0.5 m) = 275 joules of work against gravity.

Each time she lets the bar down gently, gravity does: (550 N) x (0.5 m) = 275 joules of work against her muscles. 

The bodybuilder would do exactly zero work in the process of 1-up followed by 1-down.