The coefficient of friction between an object and a surface,if we need to move an object of weight $150 \ N$ on a horizontal surface with a force of $75 \ N$,is

What is the maximum acceleration of a train such that a $50 \ kg$ box lying on its floor remains stationary (in $m \ s^{-2}$)? (Given: Coefficient of static friction between the box and the train's floor is $0.3$ and $g = 10 \ m \ s^{-2}$)

$A$ wooden block of mass $M$ lies on a rough floor. Another wooden block of the same mass is hanging from the point $O$ through strings as shown in the figure. To achieve equilibrium,the coefficient of static friction between the block on the floor and the floor itself is:

What is friction? What is impending motion?

Block $B$ lying on a table weighs $W$. The coefficient of static friction between the block and the table is $\mu$. Assume that the cord between $B$ and the knot is horizontal. The maximum weight of the block $A$ for which the system will be stationary is

$A$ block of mass $m$ lying on a rough horizontal plane is acted upon by a horizontal force $P$ and another force $Q$ inclined at an angle $\theta$ to the vertical. The minimum value of the coefficient of friction between the block and the surface for which the block will remain in equilibrium is