• # question_answer In the figure, the ball P is released from rest, when the spring is at its natural length. For the  block Q of mass $2{{m}_{0}}$to leave contact with ground at some stage, the minimum mass of P must be A)  ${{m}_{0}}$ B) $2{{m}_{0}}$ C)  ${{m}_{0}}/2$ D)  ${{m}_{0}}/4$

The block will experience maximum upward force, when the ball P is at its lowest position (x). Energy conservation gives            $mgx=\frac{1}{2}k{{x}^{2}}$or $x=2mg/k$ ?(i) For the block Q to leave contact $kx=2\,{{m}_{0}}g$ Solving Eqs. (i) and (ii), we get $m=2{{m}_{0}}/2={{m}_{0}}$