$A$ block is projected with speed $20 \,m/s$ on a rough horizontal surface. The coefficient of friction $(\mu)$ between the surfaces varies with time $(t)$ as shown in the figure. The speed of the body at the end of $4 \,s$ will be ............ $m/s$ $(g = 10 \,m/s^2)$.

$A$ 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 coefficients of static and kinetic friction for a block on a rough surface are $0.6$ and $0.4$ respectively. The minimum force required to set the block in motion is $64 \, N$. If this force continues to be applied after the block starts moving,what will be the acceleration of the block?

$A$ 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 of mass $1 \,kg$ is moving with a velocity $10 \,ms^{-1}$ on a horizontal rough surface having a coefficient of kinetic friction $0.4$. If the constant force is removed, the body comes to rest in a time (Acceleration due to gravity $g = 10 \,ms^{-2}$). (in $\,s$)

$A$ block of mass $m$ rests on a rough horizontal surface as shown in the figure. The coefficient of friction between the block and the surface is $\mu$. $A$ force $F = mg$ acting at an angle $\theta$ with the vertical side of the block pulls it. In which of the following cases can the block be pulled along the surface?