A mass m is revolving in a vertical circle at the end of a string of length 20 cm. By how much does the tension of the string at the lowest point exceed the tension at the top most point?

Options

A. 2 mg
B. 4 mg
C. 6 mg
D. 8 mg

Answer

C

Explanation

`T_1-mg=("mu"^2)/(l)` …..(i)
`T_2+mg=(mv^2)/(l)` ….(ii)

and `0+1/2"mu"^2=mg2l+1/2mv^2`
(i-ii)`T_1-T-2=m/l(u^2-v^2)+2mg`
=`m/l(4gf)`+2 mg
`T_1-T_2`=6 mg