$A$ block of mass $M$ is being pulled along a rough horizontal surface. The coefficient of friction between the block and the surface is $\mu$. If another block of mass $M/2$ is placed on the block and it is again pulled on the surface,the coefficient of friction between the block and the surface will be

$A$ 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

$A$ person initially at rest starts walking towards the east without slipping or skidding. What is the type of friction acting on the person from the ground, and in which direction does the frictional force act?

$A$ heavy box is to be dragged along a rough horizontal floor. Person $A$ pushes it at an angle of $30^\circ$ from the horizontal and requires a minimum force $F_A$. Person $B$ pulls the box at an angle of $60^\circ$ from the horizontal and needs a minimum force $F_B$. If the coefficient of friction between the box and the floor is $\mu = \frac{\sqrt{3}}{5}$,find the ratio $\frac{F_A}{F_B}$.

The maximum value of the applied force $F$ such that the block as shown in the arrangement does not move is (Acceleration due to gravity, $g=10 \,ms^{-2}$) (in $\,N$)

$A$ person is using scissors to cut a wire of circular cross-section and negligible weight. The wire slides in the direction away from the hinge until the angle between the scissors blades becomes $2 \alpha$. The friction coefficient between the blades and the wire is: