Question

While spinning down from 500.0 rpm to rest, a solid uniform flywheel does 5.1 kJ of work. If the radius of the disk is 1.2 m, what is its mass?

Answer 1

Answer:

Mass will be equal to 5.173 kg

Explanation:

Energy due to rotation of uniform flywheel is E = 5.1 KJ = 5100 J

Angular speed $\omega =500rpm=\frac{2\times 3.14\times 500}{60}=52.33rad/sec$

Radius r = 1.2 m

Rotational kinetic energy of flywheel is $E=\frac{1}{2}I\omega ^2$

So $5100=\frac{1}{2}\times I\times 52.33 ^2$

$I=3.724kgm^2$

Moment of inertia of solid flywheel is $I=\frac{1}{2}mr^2$

So $3.724=\frac{1}{2}\times m\times 1.2^2$

$m=5.173kg$

So mass will be equal to 5.173 kg