If the normal reaction is $R$ and the coefficient of friction is $\mu$,what is the work done against friction in moving a body by a distance $d$ slowly?

The magnitude of acceleration of a block moving with a speed of $10\,m/s$ on a rough surface is $.........\,m/s^2$,if the coefficient of friction is $0.2$.

$A$ boat of mass $700 \,kg$ is travelling at a speed of $24 \,ms^{-1}$ when its engine is shut off. The magnitude of frictional force $f$ between the boat and water is given by $f = 35v$, where $v$ is the speed in $ms^{-1}$ and $f$ is in newton. Find the time taken for the speed of the boat to become $6 \,ms^{-1}$. (in $\,s$)

$A$ block of mass $40 \,kg$ slides over a surface,when a mass of $4 \,kg$ is suspended through an inextensible massless string passing over a frictionless pulley as shown below. The coefficient of kinetic friction between the surface and the block is $0.02$. The acceleration of the block is ............ $m/s^2$. (Given $g = 10 \,m/s^2$.)

$A$ uniform chain of length $L$ is lying on a horizontal table. If the coefficient of friction between the chain and the table top is $\mu$,what is the maximum length of the chain that can hang over the edge of the table without disturbing the rest of the chain on the table?

$A$ conveyor belt is moving horizontally with a velocity of $2 \,m \,s^{-1}$. If a body of mass $10 \,kg$ is kept on it, then the distance travelled by the body before coming to rest relative to the belt is (The coefficient of kinetic friction between the belt and the body is $0.2$ and acceleration due to gravity is $10 \,m \,s^{-2}$) (in $\,m$)