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 the car is

Answer 1

(mv^2)/r=mg

(v^2)=rg

v=root(rg)

v=root(20×4.9×2)

v=root(2×7×7×2)

v=14m/s

Answer 2

$weight = mg \\ n = mg \div 2 \\ mg - \frac{mg}{2} = m {v }^{2} \div r \\ mg \div 2 = m {v}^{2} \div r \\ g \div 2 = {v}^{2} \div r \\ {v}^{2} = 50 \\ v = \sqrt{50}m {s}^{ - 1}$