A metallic chain $1 \mathrm{m}$ long lies on a horizontal surface of a table. The chain starts sliding on the table if $25 \mathrm{cm}$ (or more of it) hangs over the edge of a table. The correct value of the coefficient of friction between the table and the chain is

In the figure shown, the coefficient of static friction between the block $\mathrm{A}$ of mass $20 \mathrm{kg}$ and horizontal table is $0.2.$ What should be the minimum mass of hanging block just beyond which blocks start moving?

In the following figure, the object of mass $m$ is held at rest by a horizontal force as shown. The force exerted by the string on the block is

$\mathrm{Mr}. A, B$ and $C$ are trying to put a heavy piston into a cylinder at a mechanical workshop in railway yard. If they apply forces $F_1, F_2$ and $F_3$ respectively on ropes then for which set of forces at that instant, they will be able to perform the said job?

A horizontal force $10 N$ is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is $0.2,$ the weight of the block is