Answer (3)
Sol. From the frame of truck
$
\begin{array}{l}
\operatorname{Tsin} \theta=\mathbf{m a} \\
T \cos \theta=\mathrm{mg}
\end{array}
$
$\theta=\tan ^{-1}\left(\frac{\mathbf{a}}{g}\right)$
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 (1) to the left and angle of inclination of the pendulum with the vertical is $\tan ^{-1}\left(\frac{\mathbf{g}}{\mathbf{a}}\right)$ (2) to the left and angle of inclination of the pendulum with the vertical is $\sin ^{-1}(\underline{\mathbf{g}}{\mathrm{a}})$(3) to the left and angle of inclination of tha pendulum with the vertical is $\tan ^{-1}\left(\frac{\mathbf{a}}{\mathbf{g}}\right)$ (4) to the left and angle of inclination of the pendulum with the vertical is $\sin ^{-1}\left(\frac{\mathbf{a}}{\mathbf{g}}\right)$
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 (1) to the left and angle of inclination of the pendulum with the vertical is $\tan ^{-1}\left(\frac{\mathbf{g}}{\mathbf{a}}\right)$ (2) to the left and angle of inclination of the pendulum with the vertical is $\sin ^{-1}(\underline{\mathbf{g}}{\mathrm{a}})$(3) to the left and angle of inclination of tha pendulum with the vertical is $\tan ^{-1}\left(\frac{\mathbf{a}}{\mathbf{g}}\right)$ (4) to the left and angle of inclination of the pendulum with the vertical is $\sin ^{-1}\left(\frac{\mathbf{a}}{\mathbf{g}}\right)$