A point mass 'm' is moved in a vertical circle of radius 'r' with the help of a string. The velocity of the mass is $\sqrt{7gr}$ at the lowest point. The tension in the string at the lowest point is

A 1 mg

B 6 mg

C 7 mg

D 8 mg

The answer is D.

Solution

At the lowest point, $T-mg=\dfrac{mv^2}{r}=\dfrac{m(7gr)}{r}=7mg\Rightarrow T=7mg+mg=8mg$.

Concept Vertical circular motion - tension at the lowest point

72 questions from this chapter have appeared across 27 exam years.