Question

A car is moving with a constant speed of $20\, m / s$ in a circular horizontal track of radius $40\, m$. A bob is suspended from the roof of the car by a massless string. The angle made by the string with the vertical will be : (Take $g=10 \, m / s ^2$ )

• A. $\frac{\pi}{6}$
• B. $\frac{\pi}{2}$
• C. $\frac{\pi}{4}$
• D. $\frac{\pi}{3}$

Answer 1

Answer: (C)

$ T \sin \theta=\frac{ mv^2}{ R } $
$ \tan \theta=\frac{ v ^2}{ Rg }$
$ \tan \theta=\frac{20^2}{40 \times 10}$
$ \tan \theta=1$
$\Rightarrow \theta=\frac{\pi}{4}$