A block of mass$m$ is released from rest. Initially the spring is unstretched. The pulley and strings are ideal. The maximum energy stored in the spring is

A ball of mass $m$ moving with some velocity hits two stationary balls of same dimensions as striking ball but each of mass $2m$ symmetrically and simultaneously. If striking ball comes to rest after collision, then coefficient of restitution is

A variable force $\overrightarrow{F}=\left(x^2\hat{i}+xy\hat{j}\right)\mathrm{N}$ is acting on a particle which moves from point$(0,0)$ to $(1 \mathrm{m},2 \mathrm{m})$ along the path$OAB$ as shown. Find work done by force.

A particle of mass$m$ is moved slowly from point $A$ to$B$ along a rough curvilinear path $AOB$ as shown. If coefficient of friction is $\mu$, then work done by frictional force acting on particle will be

If mass $m$ is released when both springs were relaxed, then what is the maximum displacement of point $P$ (junction point of two spring) shown in figure. 

A block of mass $10 \mathrm{kg}$ is hanging over a smooth and light pulley through a light string and the other end of the string is pulled down by a constant force $F$. The kinetic energy of the block increases by $20 \mathrm{J}$ in $1 \mathrm{s}$