Question

A simple pendulum is suspended by the roof of a car. If the car is moving with a uniform horizontal velocity, $V$, then the string makes an angle '$\theta$ ' with the vertical. '$\theta$ ' will be equal to :

• A. $\frac{V}{g}$
• B. $\frac{V^2}{g}$
• C. $Vg$
• D. $zero$

Answer 1

Answer: (D)

$zero$

As seen in the FBD, we have the string making an angle $\theta$ with the vertical, tension in the string being $T$ and weight of the ball being $mg$.
Breaking the tension in the string along vertical and horizontal directions we have following equations;
$Tcos\theta =mg$ --------- 1
$Tsin\theta =ma$ --------- 2
Since car is moving with a uniform velocity, we have $a=0$.
Putting this value in equation 2 gives $sin\theta =0$.
Only possible value of $\theta =0$