Answer to Question #310032 in Mechanics | Relativity for Olen

Question

A flywheel has a moment of inertia of 4.8 kg-m2 . What constant force is required to increase its

frequency from 3 rev/s to 6 rev/s in 7 revolutions?

Answer 1

Calculations

$\qquad\qquad \begin{aligned} \small \tau &=\small I\alpha \cdots(1)\\ \\ \small w^2_1&=\small \omega^2_2+2\alpha \theta\\ \small 6^2&=\small 3^2+2\alpha \times7\\ \small \alpha&=\small 1.93\,rads^{-2}\\ \\ \small \text{In (1),}\\ \\ \small \tau&=\small 4.8\,kgm^2\times1.93s^{-2}\\ \small F\times r&=\small 9.26\\ \small F&=\small \frac{9.26}{r} \end{aligned}$

• Once you know the radius or diameter of the flywheel the needed force can be calculated.