$A$ block of mass $50\, kg$ slides over a horizontal distance of $1\, m$. If the coefficient of friction between their surfaces is $0.2$,then the work done against friction is ......... $J$.

$A$ block of mass $0.5 \ kg$ is at rest on a horizontal table. The coefficient of kinetic friction between the table and the block is $0.2$. If a horizontal force of $5 \ N$ is applied on the block,the kinetic energy of the block in a time of $4 \ s$ is (Acceleration due to gravity $= 10 \ m/s^2$). (in $J$)

$A$ horizontal force of $129.4 \, N$ is applied on a $10 \, kg$ block which rests on a horizontal surface. If the coefficient of friction is $0.3$,the acceleration should be ....... $m/s^2$.

The blocks shown in the figure move with a constant velocity of $10 \, m/s$ towards the right. All surfaces in contact are rough. The friction force applied by the ground on block $B$ is ........ $N$.

$A$ body of mass $2$ kg is moving on the ground and comes to rest after some time. The coefficient of kinetic friction between the body and the ground is $0.2$. The retardation in the body is ...... $m/s^2$.

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 $0.2$.