Find the work done against friction in $J$ when a block of mass $50\, kg$ moves a distance of $1\, m$ on a rough horizontal surface with a coefficient of friction of $0.2$.

$A$ body of mass $2\, kg$ is being dragged with uniform velocity of $2\, m/s$ on a rough horizontal plane. The coefficient of friction between the body and the surface is $0.20$. The amount of heat generated in $5\, s$ is ........ $cal$ $(J = 4.2\, J/cal$ and $g = 9.8\, m/s^2)$

$A$ small body slips,subject to the force of friction,from point $A$ to point $B$ along two curved surfaces of equal radius,first along route $1$,then along route $2$. Friction does not depend on the speed and the coefficient of friction on both routes is the same. In which case will the body's speed at $B$ be greater?

$A$ horizontal force of $40\,N$ is applied to a $5\,kg$ block which is at rest on a horizontal surface. If the coefficient of kinetic friction is $0.4$,then the acceleration of the block is ........ $m/s^2$ $(g = 10\,m/s^2)$.

$A$ block of mass $m=2 \ kg$ is initially at rest on a horizontal surface. $A$ horizontal force $F_1=(6 \ N) \hat{i}$ and a vertical force $F_2=(10 \ N) \hat{j}$ are then applied to the block. The coefficients of static friction and kinetic friction for the block and the surface are $0.4$ and $0.25$, respectively. The magnitude of the frictional force acting on the block is (assume $g=10 \ m/s^2$): (in $N$)

Two blocks $A$ and $B$ of masses $2 \ kg$ and $4 \ kg$ respectively are kept on a rough horizontal surface. If the same force of $20 \ N$ is applied on each block,then the ratio of the accelerations of the blocks $A$ and $B$ is (Coefficient of kinetic friction between the surface and the blocks is $0.3$ and acceleration due to gravity $= 10 \ m \ s^{-2}$).