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A mass 2 kg is whirled in a horizontal c...

A mass 2 kg is whirled in a horizontal circle by means of a string at an initial speed of 5 revolutions per minute . Keeping the radius constant the tension in the string is doubled. The new speed is nearly

A

14 rpm

B

10 rpm

C

2.25 rpm

D

7 rpm

Text Solution

Verified by Experts

The correct Answer is:
D
Tension in the string
`T = momega^(2)r = m(2pi N)^(2)r = 4pi^(2)mN^(2)r`
`T prop N^(2) rArr N_(1)/N_(2) = sqrt(T_(1)/T_(2))`
`rArr 5/N_(2) = sqrt(T/(2T)) rArr N_(2) = 5sqrt(2) = 7` rpm
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