Two masses $m$ and $M$ are attached to the strings as shown in the figure. If the system is in equilibrium, then

A mass of $10\,kg$ is suspended vertically by a rope from the roof. When a horizontal force is applied on the rope at some point, the rope deviated at an angle of $45^o$ at the roof point. If the suspended mass is at equilibrium, the magnitude of the force applied is ……….  $N$ $(g = 10\,ms^{-2})$ 

A football of radius $R$ is kept on a hole of radius $r (r < R)$ made on a plank kept horizontally. One end of the plank is now lifted so that it gets tilted making an angle $\theta$ from the horizontal as shown in the figure below. The maximum value of $\theta$ so that the football does not start rolling down the plank satisfies (figure is schematic and not drawn to scale) –

Explain primary concept of force.

Two masses $m$ and $M$ are attached to the strings as shown in the figure. If the system is in equilibrium, then