A ball of mass 100 g is dropped from a height h =10 cm on a platform fixed at the top of a vertical spring (as shown in figure). The ball stays on…

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