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

Options

A. `tan^(-1)""((g)/(a))`
B. `tan^(-1)""((a)/(g))`
C. `sin^(-1)""((a)/(g))`
D. `cos^(-1)""((a)/(g))`

Answer

B

Explanation

The plumb line hangs vertically when the train is at rest. When the train is accelerated, the plumb line remains along the resultant of a and g. It is along OC. It is inclined at an angle `theta` such that
`tan theta =(a)/(g)" or "theta = tan^(-1)""((a)/(g))`