# Help me find angular velocity and change in Kinetic Energy

1. Jun 23, 2005

### samemikejones

got a real tricky but fun problem, wheel A is going 35 rad/s, with I = 25 Kg*m2 and merges into wheel B with I = 15 Kg*m2, if they stick together at contact, find its angular velocity and change in Kinetic Energy...

So far, I have L = IW, or 8.8 x 10^2 kg m2/sec

and L = IW for oval to be at 9.8 x 10^2 kg m2/sec,

w = L/I

2. Jun 23, 2005

### OlderDan

Your first computation for the angular momentum looks fine. I have no idea where your second line comes from. The problem is not specific, but I assume they indend for you to assume wheel B starts at rest. The two wheels together have greater moment of inertial than either one separately. Angular momentum must be conserved. How do calculate the kinetic energy?

3. Jun 24, 2005

### OlderDan

OK, so you have an initial $$\omega$$ for each wheel. Use conservation of angular momentum to find their final $$\omega$$ and calculate the initial and final energies.