Question

A ball of mass 0.1 Kg. is whirled in a horizontal circle of radius 1 m. by means of a string at an initial speed of 10 R.P.M. Keeping the radius constant, the tension in the string is reduced to one quarter of its initial value. The new speed is

• A. 5 r.p.m.
• B. 10 r.p.m.
• C. 20 r.p.m.
• D. 14 r.p.m.

Answer 1

The correct option is A

5 r.p.m.

$T=m{\omega }^{2}r\Rightarrow \omega \propto \sqrt{T}\therefore \frac{{\omega }_2}{{\omega }_1}=\sqrt{\frac{1}{4}}\Rightarrow {\omega }_2=\frac{{\omega }_1}{2}=5rpm$