In the push-up, the athlete's weight (or force) of 250 N moves through a distance of 20 cm.
By definition,
Work = force * distance.
Therefore, work done in one push-up is
[tex]W=(250 \, N)*(20 \, cm)*(10^{-2} \, \frac{cm}{m}) = 50 \, J [/tex]
Note that 1 J = 1 N-m.
Answer: 1 J