A block of mass $5 \mathrm{kg}$ is placed on a horizontal surface and a pushing force $20 \mathrm{N}$ is acting on the back as shown in the figure. If the coefficient of friction between block and surface is $0.2$, then calculate frictional force and speed of the block after $15 \mathrm{s}$. (Given $g=10 \mathrm{m} {\mathrm{s}}^{-2}$)

A wooden block of mass $m$ resting on a rough horizontal table (coefficient of friction$=\mu$) is pulled by a force $F$ as shown in the figure. The acceleration of the block moving horizontally is

A block of mass $M=5 \mathrm{kg}$ is resting on a rough horizontal surface for which the coefficient of friction is $0.2$. When a force $F=40 \mathrm{N}$ is applied, the acceleration of the block will be $\left(g=10 \mathrm{m} {\mathrm{s}}^{-2}\right)$