Single Choice

A plumb line is suspended from a ceiling of a car moving with horizontal acceleration of $$a$$. What will be the angle of inclination with vertical.

A$$\tan^{-1} (a/g)$$
Correct Answer
B$$\tan^{-1} (g/a)$$
C$$\cos^{-1} (a/g)$$
D$$\cos^{-1} (g/a)$$

Solution

When car moves towards right with acceleration a than due to pseudo force the plumb line will tilt in backward direction making an angle $$\theta $$ with vertical
from the figure$$:-$$
$$\begin{array}{l} \tan \theta =a/g \\ \therefore \theta ={ \tan ^{ -1 } }\left( { a/g } \right) \end{array}$$
Hence,
option $$(A)$$ is correct answer.

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