A weightless string can support a tension up to $30 \mathrm{~N}$. A stone of mass $0.5 \mathrm{~kg}$ is tied…

A weightless string can support a tension up to $30 \mathrm{~N}$. A stone of mass $0.5 \mathrm{~kg}$ is tied to its one end and is revolved in a circular path of radius $2 \mathrm{~m}$ in a vertical plane. Then the maximum angular velocity of the stone will be (acceleration due to gravity $g=10 \mathrm{~m} / \mathrm{s}^2$ )
  1. $10 \mathrm{rad} / \mathrm{s}$
  2. $\sqrt{60} \mathrm{rad} / \mathrm{s}$
  3. $\sqrt{30} \mathrm{rad} / \mathrm{s}$
  4. $5 \mathrm{rad} / \mathrm{s}$

Solution

Considering force balance: $\begin{aligned} & T_{\max }=m \omega_{\max }^2 r+m g \\ & \Rightarrow \frac{T_{\text {max }}}{m}=\omega_{\max }^2 r+g \\ & \Rightarrow \frac{30 \mathrm{~N}}{0.5 \mathrm{~kg}}-10 \mathrm{~m} / \mathrm{s}^2=\omega_{\max }^2 r \\ & \Rightarrow \omega_{\max }=\sqrt{\frac{50}{2}}=5 \mathrm{rad} / \mathrm{s}\end{aligned}$ .

Asked in: MHT CET 2022 (06 Aug Shift 1)

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