Question

A bob is whirled in a horizontal plane by means of a string with an initial speed of ω rpm. The tension in the string is T. If speed becomes 2ω while keeping the same radius, the tension in the string becomes:

• A. T
• B. 4T
• C. $\frac{T}{4}$
• D. √2T

Answer 1

Answer: (B)

4T

Answer 2

Tension in the string is proportional to the square of the velocity:
$T \propto v^2$.
If $v \to 2v$, then $T \to 4T$.