Question

A car is going on an overbridge of radius $R$, maintaining a constant speed. As the car is descending on the overbridge from point B to C, the normal force on it :

• A. increases
• B. decreases
• C. remains constant
• D. first increases then decreases

Answer 1

The correct option is B decreases

Let the speed of the car be $v$ and normal reaction acting on the car be $N^{\prime }$.

Using circular motion equation for the car :

$\frac{m{v}^2}{R}=mg\cos \theta -N^{\prime }$

$⟹$ $N^{\prime }=mg\cos \theta -\frac{m{v}^2}{R}$

As the car moves from point B to C, $\theta$ changes from $0^o$ to ${90}^o$.

As cosine is a decreasing function from $0^o$ to ${90}^o$, thus $N^{\prime }$ decreases when the car moves from B to C.