Fundamentally, the normal force between two surfaces in contact is:

1. Electromagnetic

2. Gravitational

3. Weak nuclear force

4. Strong nuclear force

The pulleys and strings shown in the figure are smooth and of negligible mass. For the system to remain in equilibrium, the angle $\theta$ should be: 
 
1. $0^\circ$
2. $30^\circ$
3. $45^\circ$
4. $60^\circ$

A body of mass $5$ kg is suspended by the strings making angles $60^\circ$ and $30^\circ$ with the horizontal.

 
Then:

A man of mass $60$ kg is standing on the ground and holding a string passing over a system of ideal pulleys. A mass of $10$ kg is hanging over a light pulley such that the system is in equilibrium. The force exerted by the ground on the man is: ($g=$ acceleration due to gravity)

1. $20g$
2. $45g$
3. $40g$
4. $60g$

A string of negligible mass going over a clamped pulley of mass $m$ supports a block of mass $M$ as shown in the figure. The force on the pulley by the clamp is given by:
 
1. $\sqrt{2} M g$
2. $\sqrt{2} m g$
3. $g\sqrt{\left( M + m \right)^{2} + m^{2}}$
4. $g\sqrt{\left(M + m \right)^{2} + M^{2}}$

Choose the incorrect alternative:

The force $F$ acting on a particle of mass $m$ is indicated by the force-time graph shown below. The change in momentum of the particle over the time interval from $0$ to $8$ s is:

1. $24~\text{N-s}$
2. $20~\text{N-s}$
3. $12~\text{N-s}$
4. $6~\text{N-s}$

On the application of an impulsive force, a sphere of mass $500$ grams starts moving with an acceleration of $10$ m/s². The force acts on it for $0.5$ s. The gain in the momentum of the sphere will be:
1. $2.5$ kg-m/s
2. $5$ kg-m/s
3. $0.05$ kg-m/s
4. $25$ kg-m/s

A rigid ball of mass $M$ strikes a rigid wall at $60^{\circ}$ and gets reflected without loss of speed, as shown in the figure. The value of the impulse imparted by the wall on the ball will be: