Question

If the over-bridge is concave instead of being convex, the thrust on the road at the lowest position will be:

• A. $mg-\frac{m{v}^2}{r}$
• B. $mg+\frac{m{v}^2}{r}$
• C. $\frac{v^{2}g}{r}$
• D. $\frac{m^2{v}^{2}g}{r}$

Answer 1

The correct option is B $mg+\frac{m{v}^2}{r}$

Let the thrust on the road be $F_c$.

Then road will also push the car with same force $F_c$.

The net force on the car is centripetal force towards the center:
$\frac{m{v}^2}{r}=F_c-mg\Rightarrow F_c=mg+\frac{m{v}^2}{r}$