Question

A balloon of mass 'm' is decending down with an acceleration 'a'. How much mass should be removed from it so that it starts moving up with an acceleration 'a'

Answer 1

Take upward direction to be the positive y-direction. If m is the mass thrown out, then the equation of motion for before and after the mass m is thrown out are Ma = F – Mg

(M–m)a = F – (M–m)g

Solving the two equations m =2ma/(a+g)