# Homework Help: Rotating parts of a motor have a moment of inertia

1. May 22, 2014

### Busybee12

1. The problem statement, all variables and given/known data

The rotating parts of a motor have a moment of inertia of 15 kgm^2 and an optimum running speed of 1400 rev/min. When operating the motor is connected at optimum speed , by means of a clutch, to a shaft which has a counter rotation of 600 rev/min. The shaft has a mass of 80 kg and a solid diameter of 1200 mm.

i) Find the common speed of rotation of the two shafts, immediately after slippage has finished.
ii) Determine the change in angular momentum of the motor as the common speed is reached.
iii) Determine the change in angular kinetic energy of the motor as the common speed is reached.
iv) If the motor sends a torque of 220 Nm, find how long it will take for the system to regain optimum running speed for the motor.

2. Relevant equations

I1ω1=I2ω2?

3. The attempt at a solution

I have tried converting rev/min to rad/s and then trying to find out the common speed using angular momentum but don't know if is right?

2. May 22, 2014

### SteamKing

Staff Emeritus
Well how are we supposed to know if you don't show your calculations?