Question

A car is travelling along a flyover bridge which is a part of vertical circle of radius $10m$. At the highest point of it if the normal reaction on the car is half of its weight, the speed of car is:

• A. $7m/s$
• B. $10m/s$
• C. $14m/s$
• D. $20m/s$

Answer 1

The correct option is A $7m/s$

Normal reaction is half its weight
$\Rightarrow N=\frac{mg}{2}$
Net force which provides centripetal force is
$mg-\frac{mg}{2}=\frac{m{v}^2}{R}$
$\to v=\sqrt{\frac{Rg}{2}}=\sqrt{\frac{9.8\times 10}{2}}=7m/s$