Question

A force starts acting on a spring block system. At a stretch when $x=\frac{mg}{k}$ ( $W_{F_{ext}}$ and $W_{F_s}$ are works done by $F_{ext}$ and spring force)

• A. $W_{F_{ext}}+W_{F_s}=0$
• B. $W_{F_{ext}}=\frac{1}{2}k{x}^2$
• C. $W_{F_{ext}}+W_{F_s}>0$
• D. $W_{F_{ext}}+W_{F_s}<0$

Answer 1

The correct option is C $W_{F_{ext}}+W_{F_s}>0$

Till the position shown, the spring force increases but the external force is constant. Hence there is a net force acting till $x=\frac{mg}{k}$