If a ladder weighing $250\,N$ is placed against a smooth vertical wall having coefficient of friction between it and floor is $0.3$, then what is the maximum force of friction available at the point of contact between the ladder and the floor ........ $N$

For the given figure, if block remains in equilibrium position then find frictional force between block and wall ........ $N$ 

A rectangular block has a square base measuring $a \times a$ and its height is $h$. It moves on a  horizontal surface in a direction perpendicular to one of the edges.  The coefficient of  friction is $\mu$. It will topple if

$A$ block $P$ of mass m is placed on a frictionless horizontal surface. Another block Q of same mass is kept on $P$ and connected to the wall with the help of a spring of spring constant k as shown in the figure. ${\mu _s}$ is the coefficient of friction between$  P$ and $ Q$. The blocks move together performing SHM of amplitude $A$. The maximum value of the friction force between $P$ and $Q$ is

In the given figure the acceleration of $M$ is $(g = 10 \,ms^{-2})$

Maximum force of friction is called