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

1. Electromagnetic

2. Gravitational

3. Weak nuclear force

4. Strong nuclear force

A particle of mass m is suspended from a ceiling through a massless string. The particle moves in a horizontal circle as shown in the given figure. The tension in the string is:
 

1. mg

2. 2mg

3. 3mg

4. 4mg

Choose the incorrect alternative:

A block slides down on a 45° rough incline in thrice the time it takes to slide down on a frictionless 45° incline of the same length. The coefficient of friction between the block and the rough incline is:

The kinetic energy 'K' of a particle moving in a circular path varies with the distance covered S as K = a${\mathrm{S}}^2$, where a is constant. The angle between the tangential force and the net force acting on the particle is: (R is the radius of the circular path)

1.  ${\tan }^{-1}\left(\frac{\mathrm{S}}{\mathrm{R}}\right)$

2.  ${\tan }^{-1}\left(\frac{\mathrm{R}}{\mathrm{S}}\right)$

3.  ${\tan }^{-1}\left(\frac{\mathrm{a}}{\mathrm{R}}\right)$

4.  ${\tan }^{-1}\left(\frac{\mathrm{R}}{\mathrm{a}}\right)$

The tension in the string connecting blocks, B and C, placed on a smooth horizontal surface in the following diagram is:

If two forces ($6\hat{\mathrm{i}}$ $+$ $8\hat{\mathrm{j}}$) and ($4\hat{\mathrm{i}}$ $+$ $4\hat{\mathrm{j}}$) N are acting on a body of mass 2 kg, then the acceleration produced in the body in $\mathrm{m}/{\mathrm{s}}^2$ will be:

1. ($5\hat{\mathrm{i}}$ $+$ $6\hat{\mathrm{j}}$)

2. ($10\hat{\mathrm{i}}$ $+$ $12\hat{\mathrm{j}}$)

3. ($6\hat{\mathrm{i}}$ $+$ $12\hat{\mathrm{j}}$)

4. ($2\hat{\mathrm{i}}$ $+$ $3\hat{\mathrm{j}}$)

The friction between the front foot and the back foot when walking on a horizontal surface is, respectively:

1. Forward, forward

2. Backward, backward

3. Forward, backward

4. Backward, forward

A simple pendulum hangs from the roof of a train moving on horizontal rails. If the string is inclined towards the front of the train, then the train is:

1. moving with constant velocity.

2. in accelerated motion.

3. in retarded motion.

4. at rest.

A block of mass M is pulled by a force F, making an angle $\mathrm{\theta }$ with the horizontal on a smooth horizontal surface as shown. If a is the acceleration of block on the surface, then the contact force between the block and the surface will be:
        
1. Mg + Macos$\mathrm{\theta }$

2. Mg - Macos$\mathrm{\theta }$

3. Mg + Matan$\mathrm{\theta }$

4. Mg - Matan$\mathrm{\theta }$