A point mass m is moved in a vertical circle of the radius r with the help of a string. The velocity of the mass is 7 g r at the lowest point. The tension in the string at the lowest point is:NEET 202

Question

A point mass m is moved in a vertical circle of the radius r with the help of a string. The velocity of the mass is 7 g r at the lowest point. The tension in the string at the lowest point is:NEET 2020 (Phase 2)

TestHub · Accepted Answer

First, make the free body diagram when a mass bob is attached with a string of length, $r$ rotating in a vertical circle.

Given, $v = \sqrt{7 g r}$ , now make the equation between centripetal force and surface tension which are acted in opposite direction,

$\Rightarrow T - m g = \frac{m (\sqrt{7 g r})^{2}}{r}$ $\Rightarrow T = 8 m g$ .

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