P. 3994. A 60 kg boy notices a nice fruit on a tree. Even with stretched arms he cannot reach it, he is a 0.5 m below the fruit. The boy crouches down - his centre of mass descends 0.4 m - and then he leaps up. Thus he just reaches the fruit. Assume that he exerts a constant force on the ground while he touches it.
a) What is this force at least?
b) What is the average power of the boy?