Q: A balloon of mass M is descending at a constant acceleration a. When a mass m is released from the balloon it starts rising with the same acceleration a. Assuming that its volume does not change, what is the value of m ?
(a) a/(a+g) M
(b) 2a/(a+g) M
(c) (a+g)/a M
(d) (a+g)/2a M
Ans: (b)