The rotor of an electric motor has a rotational inertia of 45 kg/m2. what is its kinetic energy if it turns at 1500 rev/min?

Question

45 kg/m² is the proper way of writting it

Answer 1

From earlier physics we have regular or "linear" or "non-rotational" KE = (1/2) Mass * Velocity squared

 

so I, or moment of inertia is just "rotational" mass and we write the "rotational" kinetic energy equation

 

rotational KE = (1/2) I [(angular velocity)^2]

 

so square 1500 rev/min, then multiply times I=45 kg/m2, then multiply by 1/2

 

So, although a mass may not be moving from one location is space to another, if it is spinning, then that spinning motion will give it a "spinning" kinetic energy or a spinning "energy of motion"