A plank with a box on it at one end is gradually raised about the other end. As the angle of inclination with the horizontal reaches $30°$, the box starts to slip and slides $4.0 \mathrm{m}$ down the plank in $4.0 \mathrm{s}$. The coefficients of static and kinetic frictions between the box and the plank will be, respectively,

Given in the figure are two blocks $A$ and $B$ of weight $20 \mathrm{N}$ and$100 \mathrm{N}$, respectively. These are being pressed against a wall by a force $F$ as shown. If the coefficient of friction between the blocks is $0.1$ and between the block $B$ and the wall is$0.15$, the frictional force applied by the wall on the block $B$ is:

Two masses $m_1=5 \mathrm{kg}$ and $m_2=10 \mathrm{kg}$ connected by an inextensible string over a frictionless pulley are moving as shown in the figure. The coefficient of friction of horizontal surface is $0.15$. The minimum weight $m$ that should be put on top of $m_2$ to stop the motion is,

A block of mass $10 \mathrm{kg}$ is kept on a rough inclined plane as shown in the figure. A force of $3 \mathrm{N}$ is applied on the block. The coefficient of static friction between the plane and the block is $0.6$. What should be the minimum value of force $P$ such that the block does not move downward? (Take, $g=10 \mathrm{m} {\mathrm{s}}^{-2}$.)

A block kept on a rough inclined plane, as shown in the figure, remains at rest upto a maximum force $2 \mathrm{N}$ down the inclined plane. The maximum external force up the inclined plane that does not move the block is $10 \mathrm{N}$. The coefficient of static friction between the block and the plane is (take, $g=10 \mathrm{m} {\mathrm{s}}^{-2}$),