$A$ body of mass $2 \, kg$ is kept by pressing it against a vertical wall by a force of $100 \, N$. The coefficient of friction between the wall and the body is $0.3$. Then the frictional force is equal to ........ $N$.

For the given figure,find the acceleration of the $40\, kg$ block in $m/s^2$. (Take $g = 10\, m/s^2$)

Two blocks of masses $M_1$ and $M_2$ are connected with a string passing over a pulley as shown in the figure. The block $M_1$ lies on a horizontal surface. The coefficient of friction between the block $M_1$ and the horizontal surface is $\mu$. What additional mass $m$ should be placed on the block $M_1$ so that the system does not accelerate?

Which one of the following statements is correct?

$A$ block is kept on a rough horizontal surface. The acceleration of the block increases from $6 \ m/s^2$ to $11 \ m/s^2$ when the horizontal force acting on it increases from $20 \ N$ to $30 \ N$. The coefficient of kinetic friction between the block and the surface is (Acceleration due to gravity $g = 10 \ m/s^2$):

$A$ block of mass $M$ is moving on a rough horizontal surface with momentum $P$. The coefficient of friction between the block and the surface is $\mu$. The distance covered by the block before it stops is $[g = \text{acceleration due to gravity}]$.