Circular Motion

A vehicle is moving with a constant speed of $10 \mathrm{~m} / \mathrm{s}$ in a circular horizontal track of radius 20 m . A bob is suspended from the roof of a vehicle by a massless string. The angle made by the string with the vertical will be (acceleration due to gravity, $\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2$ )