A bodybuilder loads a bar with 550 Newtons (~125 pounds) of weight and pushes the bar over her head 10 times. Each time she lifts the weight 0.5 meters. How much work did she do?

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.

If the human physical muscular system were 100% efficient, and capable

of absorbing work as well as spending it, then the bodybuilder would do

exactly zero work in the process of 1-up followed by 1-down.

(550 N) X (0.5 m) = 275 joules