1. Tardigrade
  2. Question
  3. Physics
  4. A metal coin of mass 5 g and radius 1 cm is fixed to a thin stick AB of negligible mass as shown in the figure. The system is initially at rest. The constant torque (in Nm ) that will make the system rotate about AB at 25 rotations per second in 5 s, is close to:

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. A metal coin of mass $5 \, g$ and radius $1 \,cm$ is fixed to a thin stick $AB$ of negligible mass as shown in the figure. The system is initially at rest. The constant torque (in $Nm$ ) that will make the system rotate about $AB$ at $25$ rotations per second in $5\, s$, is close to:Physics Question Image

System of Particles and Rotational Motion

Solution:

Angular acceleration,
$\alpha=\frac{\omega-\omega_0}{t}=\frac{25 \times 2 \pi-0}{5}=10 \pi rad / s ^2$
$ \tau =I \alpha$
$ \Rightarrow \tau =\left(\frac{5}{4} m R^2\right) \alpha \approx\left(\frac{5}{4}\right)\left(5 \times 10^{-3}\right)\left(10^{-4}\right) 10 \pi$
$=2.0 \times 10^{-5} Nm $