Q.
A ball of mass $100 \,g$ is dropped from a height $h =10 \,cm$ on a platform fixed at the top of vertical spring (as shown in figure). The ball stays on the platform and the platform is depressed by a distance $\frac{ h }{2}$. The spring constant is _____$Nm ^{-1} . \left(\right.$ Use $\left.g=10 \,ms ^{-2}\right)$
Solution: