Question

A disc of mass 100 kg and radius 1 m is rotating at 300 rpm. The torque required to rotate the disc in opposite direction with same speed in time 50 second is ______.

Options

• 30π Nm

• 40π Nm

• 20π Nm

• 10π Nm

Answer 1

A disc of mass 100 kg and radius 1 m is rotating at 300 rpm. The torque required to rotate the disc in opposite direction with same speed in time 50 second is 20π Nm.

Explanation:

M= 100 kg     R = 1 m

f = 300rpm `=300/60"rps"` = 5rps

ω = 2π × 5 = 10π rad/s

t = 50 sec

τ = I α `=(1/2"MR"^2)(omega/t)=1/2xx100xx1^2xx(10pi)/50=10pi  "Nm"`

To rotate the disc in opposite direction torque required = 20π Nm