Question

A pendulum is suspended from the roof of a car. The car is moving with an acceleration of $49cm/s^2$. The angle which its string makes with the vertical is:

• A. $0^{\circ }$
• B. $3^{\circ }$
• C. ${10}^{\circ }$
• D. ${120}^{\circ }$

Answer 1

The correct option is B $3^{\circ }$

Angle made with the vertical is $\theta$
Then, $\theta ={tan}^{-1}\left(\frac{pseudoforce}{weight}\right)={tan}^{-1}\left(\frac{ma}{mg}\right)={tan}^{-1}\left(\frac{a}{g}\right)$
$\theta ={tan}^{-1}\left(\frac{49}{980}\right)={tan}^{-1}\left(0.05\right)$
$\theta =0.05radians=3^{\circ }$