Question

A car is travelling round the curve of $300m$ radius. A pendulum hanging to the ceiling of the car makes an angle of ${30}^{\circ }$ with the vertical. Then the speed of the car is (in $km/h$).

• A. $140$
• B. $150$
• C. $160$
• D. $120$

Answer 1

The correct option is B $150$

$\begin{array}{c}\tan {30}^{\circ }=\frac{v^2}{rg}\\ v^2=100.10\sqrt{3}\\ v=10\sqrt{17.32}\\ v=41.6m/s\\ v=41.6\times \frac{18}{5}km/h\\ Hence,\\ v=149.8\simeq 150km/h\end{array}$

So, option $B$ is correct answer.