Question

A body of mass $m$ is rotated at uniform speed along vertical circle with help of light string. If $T _{1}, T _{2}$ are tensions in the string when the body is crossing highest and lowest point of vertical circle respectively then which of following expression is correct.

• A. $T_{2}-T_{1}=6 \,mg$
• B. $T_{2}-T_{1}=4 \,mg$
• C. $T_{2}-T_{1}=2 \,mg$
• D. $T_{2}-T_{1}=m g$

Answer 1

Answer: (C)

$T_{1}=\frac{m v^{2}}{r}-m g$
$ T_{2}=\frac{m v^{2}}{r}+m g$
Then $T_{2}-T_{1}=2 \,mg$