Question

A ball of mass $m$ is dropped from height h on a light platform fixed at the top of vertical spring as shown in the figure. The platform is depressed by a distance $x$. What is the spring constant ?

• A. $\frac{2 mgh }{ x ^{2}}$
• B. $2 mgh + x$
• C. $\frac{2 mg ( h + x )}{ x ^{2}}$
• D. $\frac{2 mg ( h + x )}{ h ^{2}}$

Answer 1

Answer: (C)

(W.D) $g+(W . D)_{\text {spring }}=\Delta K E$
$=K_{F}-K_{i}$
$m g(h+x)-\frac{1}{2} k x^{2}=0-0$
$K=\frac{2 m g(h+x)}{x^{2}}$