$A$ block of mass $100 \ kg$ slides over a distance of $10 \ m$ on a horizontal surface. If the coefficient of friction between the surfaces is $0.4$,then the work done against friction (in $J$) is:

$A$ body is moving with a uniform velocity of $2 \, m/s$ on a rough level surface. The frictional force on it is $10 \, N$. If the body moves with a velocity of $4 \, m/s$,the force of friction will be ........ $N$.

$A$ wooden block of mass $m$ resting on a rough surface (coefficient of friction $\mu$) is pulled by a force $F$ at an angle $\theta$ with the horizontal,as shown in the figure. The acceleration of the block moving horizontally is:

$A$ block of weight $W$ is kept on a rough horizontal surface (friction coefficient $\mu$). Two forces of magnitude $W/2$ each are applied as shown in the figure. Choose the $\text{CORRECT}$ statement:

$A$ spring-block system is placed on a rough horizontal floor. The block is pulled towards the right to give the spring some elongation and then released. The block will have maximum velocity when:

$A$ 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 ........ $N$.