Consider the system shown in the figure. Coefficient of friction between the block and table is $\mu =0.5.$ The system is released from rest. Find the work done by friction, when the speed of block is $10 {\mathrm{ms}}^{-1}(m=1 \mathrm{kg})$

Find the maximum compression in the spring, if the lower block is shifted to rightwards with acceleration $a$. All the surfaces are smooth.

For a particle moving under the action of a variable force, kinetic energy-position graph is given, then