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, that will make the system rotate about AB at 25 rotations per second in 5 s, is close to :

Engineering

Physics

Instantaneous Centre and Instantaneous Axis of Rotation

Question

4.0 × 10^–6 Nm

2.0 × 10^–5 Nm

7.9 × 10^–6 Nm

1.6 × 10^–5 Nm

LiveFree JEE Main Previous Year Online Papers Live Free JEE Advance Previous Year Online Papers

College PredictorLive

Know your College Admission Chances Based on your Rank/Percentile, Category and Home State.

Get your JEE Main Personalised Report with Top Predicted Colleges in JoSA

m = 5 × 10^–3 kg, r = 10^–2 m

ω = 25 × 2π rad/5

= 50 π rad/sec

$ω = \frac{τ}{I} t$

$τ = \frac{Iω}{t} = \frac{5 {mr}^{2}}{4} \times \frac{ω}{t}$

$= \frac{5 \times 5 \times 10^{- 3} \times 10^{- 4} \times 50 π}{4 \times 5}$

$= \frac{25 π}{4} \times 10^{- 6} = 2 \times 10^{- 5}$