The coefficient of static friction, $\mu _s$ between block $A$ of mass $2\,kg$ and the table as shown in the figure is $0.2$. What would be the maximum mass value of block $B$ so that the two blocks $B$ so that the two blocks do not move? The string and the pulley are assumed to be smooth and masseless ……. $kg$ $(g = 10\,m/s^2)$

A body of mass $2 \,kg$ is kept by pressing to a vertical wall by a force of $100\, N$. The coefficient of friction between wall and body is $0.3.$ Then the frictional force is equal to …….. $N$

A body of mass $10$ kg slides along a rough horizontal surface. The coefficient of friction is $1/\sqrt 3 $. Taking $g = 10\,m/{s^2}$, the least force which acts at an angle of $30^o $ to the horizontal is …… $N$

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 co-efficient 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…….$m.$