Question

A balloon with mass 'm' is descending down with an acceleration 'a' (where a< g). How much mass should
be removed from it so that is starts moving up with an acceleration 'a'?

Answer 1

Considering,

UP direction = +ve

DOWN direction = -ve

m = initial mass

m' = final mass  F = air resistance

So, -mg+F = -ma

     -F-m'g = m'a

Solving both we get, m' = m(g-a} / (g+a)

Mass to be removed = m-m' = 2ma / (g+a)( ANSWER )