Question

A grinding wheel of mass 5.0 kg and diameter 0.4m is rotating with an angular speed of 2rev s-1. Calculate the torque which will increase its angular speed to 8 revolution persecond in 2s.

Answer 1

mass of grinding wheel , m=5 kg
diameter of grinding wheel= 0.4 m
initial angular velocity, w1= 2 rev/sec
final angular velocity,w2=8 rev/sec
time interval from initial to final velocity,t= 2 secs

torque= rotational inertia*angular acceleration

T= I*Alpha

Alpha, angular acceleration= w2-w1/t
Alpha= 3 rev/sec^2

rotational inertia= 0.5*m*r^2
I=2.5*0.04
I=0.1 kgm^2

therefore torque equals= 0.3 N.m