For a body to be in dynamic equilibrium, its:

1. momentum should be zero
2. acceleration should be zero
3. kinetic energy should be zero
4. velocity should be zero

The Velocity Ratio (VR) of a block and tackle system of two pulleys with the effort in the upward direction is:

1. 1
2. 2
3. 3
4. 4

From the figure given below, the refractive index of medium B with respect to medium A (_Aμ_B) is:

1. $\dfrac{\text {sin }45\degree}{\text {sin }30\degree} \\[1em]$
2. $\dfrac{\text {sin }30\degree}{\text {sin }45\degree} \\[1em]$
3. $\dfrac{\text {sin }45\degree}{\text {sin }60\degree} \\[1em]$
4. $\dfrac{\text {sin }60\degree}{\text {sin }45\degree} \\[1em]$

When a blackened bulb thermometer is moved beyond the red region of the visible spectrum, there is a rapid rise in the temperature. This is due to the presence of :

1. Infrared radiations
2. Ultraviolet radiations
3. X-rays
4. Radio waves