$A$ block of mass $10 \ kg$ is moving on a rough surface with a velocity $v = 4 \ m/s$ to the left. An external force $F = 20 \ N$ is applied to the right as shown in the figure. The coefficient of kinetic friction is $\mu = 0.6$. The frictional force acting on the block is ...... $N$.

When two surfaces are coated with a lubricant,then they

When the engine is switched off, a vehicle of mass $M$ is moving on a rough horizontal road with momentum $p$. If the coefficient of friction between the road and the tyres of the vehicle is $\mu_k$, what is the distance travelled by the vehicle before it comes to rest?

$A$ uniform rod of length $L$ and mass $M$ is placed on a rough horizontal surface. $A$ horizontal force $F$ is applied at one end of the rod such that the rod is just in the state of rest. The coefficient of friction varies according to the relation $\mu = Kx$,where $K$ is a positive constant and $x$ is the distance from the end where the force is not applied. Find the tension at the midpoint of the rod.

$A$ small block of mass $m$ is projected horizontally with speed $u$. The coefficient of friction between the block and the plane is given by $\mu = cx$,where $x$ is the displacement of the block on the plane. Find the maximum distance covered by the block.

$A$ uniform chain of length $L$ is lying on a horizontal table. If the coefficient of friction between the chain and the table top is $\mu$,what is the maximum length of the chain that can hang over the edge of the table without disturbing the rest of the chain on the table?