Correct Answer - Option 2 : 0.5

__Concept:__

**Velocity Ratio of a Belt Drive:**

It is the ratio between the velocities of the driver and the follower or driven. Let

d_{1} = Diameter of the driver, d_{2} = Diameter of the follower or driven,

N_{1} = Speed of driver in rpm, N_{2} = Speed of follower or driven in rpm.

Velocity Ratio (VR) = \(\frac{N_2}{N_1} = \frac{d_1}{d_2}\)

__Calculation:__

__Given:__

d_{1} = 30 cm, d_{2} = 60 cm.

VR = \(\frac{d_1}{d_2}\) = \(\frac{30}{60} = \frac{1}{2} = 0.5\)

**∴ The velocity ratio of a belt drive is 0.5**