A truck is stationary and has a bob suspended by a light string, in a frame attached to the truck. The truck suddenly moves to the right with an acceleration of a. The pendulum will tilt:
Detailed Solution
In the truck frame a pseudo force $ma$ acts to the left, so the bob tilts left. $\tan\theta=\frac{ma}{mg}=\frac{a}{g} \Rightarrow \theta=\tan^{-1}\left(\frac{a}{g}\right)$.
