Question

A spinning disk of mass 5.0 kg and radius 0.25m is rotating about an axis through its center at 400 rev/min.
a.) What is the angular velocity of the disk in rad/s?
b.) What is the moment of inertia of the disk?
c.) If it accelerates at a constant rate to 800 rev/min in 8 sec, what is its angular acceleration?
d.) What constant torque is required to produce this acceleration?
e.) When it reaches that speed, what is its kinetic energy?
f.) When it reaches that speed, what is its angular momentum? @MIT 8.01 Physics …

Answer 1

First off look at what you need and what you're given. What formulas do you know of that contain these?

For your first equation how would convert revolutions per minute to radians per second? 1 revolution is = 2pi and 1 minute is equal to 60 seconds.

Using the angular velocity from the last calculation you can easily plug in your numbers to the moment of inertia formula for angular motion.

The next part is another conversion like for velocity.

The rest should be plugging into formulas, supplied that you know what they are and how to get them. Good luck.

Answer 2

\[\omega=2\pi n\] ie =41.448rad/sec
\[i=mr ^{2}\] =0.3125kgm2
\[\tau=I \alpha\]=3.1437Nm