Question

A body of mass 0.1 kg attached at the end of a string 6 m long, is whirled in a vertical circle. The tension in the string is 6.4 N at the lowest point. What is the maximum angular velocity of the body? (g = 10 $m/s^2$)

• A. 12 rad/s
• B. 9 rad/s
• C. 6 rad/s
• D. 3 rad/s

Answer 1

The correct option is D 3 rad/s

At the lowest point

$T-mg=m{\omega }^{2}r$

$T=mg+m{\omega }^{2}r\dots \dots \dots \left(1\right)$

Here $m=0.1kg$ and $r=6m,T=6.4N$

Using values in equation (1)

$6.4=1+0.1{\omega }^2\ast 6$

${\omega }^2=\frac{5.4}{0.6}=9$

$\omega =3rad/s$