Question

A 1 kg stone attached to the end of a 60 cm chain is revolving at the rate of 3 rev/s. If after 30 s, it is making only 1 rev/s. Find the mean torque acting on it.

Options

• 0.15 N-m

• 0.32 N-m

• 0.25 N-m

• 0.20 N-m

Answer 1

0.15 N-m

Explanation:

Given, r = 60 cm = 0.6 m, m = 1 kg

ω₁ = 3 rev/s = 2π × 3 rad/s

ω₂ = 1 rev/s = 2π × 1 rad/s

t = 30 s

Torgue, `tau = lalpha = l(domega)/(dt) = mr^2(domega)/(dt)`

= `1 xx (0.6)^2 xx (2pi(3) - 2pi(1))/30` = 0.15 N-m