Q: A vehicle is travelling with uniform speed along a concave road of radius of curvature 19.6m. At lowest point of concave road if the normal reaction on the vehicle is three times its weight, the speed of vehicle is

(a) 4.9 m/s

(b) 9.8 m/s

(c) 14.7 m/s

(d) 19.6 m/s

Ans:(d)

Sol:

At lowest point,

$ \displaystyle N – m g = \frac{m v^2}{r}$

Here, N = 3 m g