The limiting friction is

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 frictionless pulley as shown below. The coefficient of kinetic friction between the surface and block is $0.02$. The acceleration of block is ............ $ms ^{-2}$ (Given $g =10 \,ms ^{-2}$.)

Consider a car moving on a straight road with a speed of $100\, m/s$. The distance at which car can be stopped, is ........ $m$. $[\mu_k = 0.5]$

On a rough horizontal surface, a body of mass $2 \,kg$ is given a velocity of $10 \,m/s$. If the coefficient of friction is $0.2$ and $g = 10\, m/{s^2}$, the body will stop after covering a distance of ........ $m$

A bag is gently dropped on a conveyor belt moving at a speed of $2\,m / s$. The coefficient of friction between the conveyor belt and bag is $0.4$ Initially, the bag slips on the belt before it stops due to friction. The distance travelled by the bag on the belt during slipping motion is $.....m$ [Take $g=10\,m / s ^{-2}$ ]

A block of mass $5\,kg$ is placed at rest on a table of rough surface. Now, if a force of $30\,N$ is applied in the direction parallel to surface of the table, the block slides through a distance of $50\,m$ in an interval of time $10\,s$. Coefficient of kinetic friction is (given, $g =10\,ms ^{-2}$)