$A$ uniform chain of $6 \, m$ length is placed on a table such that a part of its length is hanging over the edge of the table. The system is at rest. The coefficient of static friction between the chain and the surface of the table is $0.5$. The maximum length of the chain hanging from the table is.......$m.$

$A$ block of mass $1 \, kg$ is at rest on a horizontal table. The coefficient of static friction between the block and the table is $0.5$. The magnitude of the force acting upwards at an angle of $60^{\circ}$ from the horizontal that will just start the block moving is

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

$A$ $20\, kg$ block is initially at rest on a rough horizontal surface. $A$ horizontal force of $75\, N$ is required to set the block in motion. After it is in motion,a horizontal force of $60\, N$ is required to keep the block moving with constant speed. The coefficient of static friction is

$A$ horizontal force just sufficient to move a body of mass $4 \,kg$ lying on a rough horizontal surface is applied on it. The coefficients of static and kinetic friction are $0.8$ and $0.6$ respectively. If the force continues to act even after the body has started moving, the acceleration of the body is (take $g=10 \,ms^{-2}$). (in $\,ms^{-2}$)

If the normal force is doubled,the coefficient of friction is