Question

A rotating flywheel can be used as a method to store energy. If it has 2.00 x 106J of kinetic energy when rotating at 390 rads, and if a frictional torque of 4.00 Nm acts on the system, in what interval of time would the flywheel come to rest? 171 min 2 560 min 26.3 min 42.7 min

Answer 1

Solution)

Given,

K.E=2*10^6 J

Rotating speed, w=390 rad/s

Torque, T= 4Nm

We know,

KE=0.5*I*w^2

2*10^6=0.5*I*(390)^2

So, Inertia,I=26.29 kg-m^2

Now, we know

Acceleration, alpha= T/I= 4/26.29= 0.1521m/s^2

Now,

W=wo+alpha*t

390=0+(0.1521*t)

Time, t=2564.10 sec= 42.73 min (Ans)----last option

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