A body of mass 0.4 kg is whirled in a vertical circle making 2 rev/sec. If the radius of the circle is 1.2 m, then tension in the string when the body is at the top of the circle, is

Given : Mass (m) = 0.4 kg

Its frequency (n) = 2 rev/sec Radius (r) =1.2 m. We know that linear velocity of the body (v) = ωr = (2πn)r

= 2 × 3.14 × 1.2 × 2 = 15.08 m/s.

Therefore, tension in the string when the body is at the top of the circle (T)

$=\frac{{\mathrm{mv}}^2}{\mathrm{r}}-\mathrm{mg}=\frac{0.4\times (15.08{)}^2}{2}-(0.4\times 9.8)$

=45.78-3.92=41.56N