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Help me find angular velocity and change in Kinetic Energy

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...

PlEASE HELP:

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
need some guidance from here...PLEASE HELP..!!
 

OlderDan

Science Advisor
Homework Helper
3,021
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samemikejones said:
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...

PlEASE HELP:

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
need some guidance from here...PLEASE HELP..!!
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?
 

OlderDan

Science Advisor
Homework Helper
3,021
1
samemikejones said:
K.E. = 1/2 I omegah squared
OK, so you have an initial [tex] \omega [/tex] for each wheel. Use conservation of angular momentum to find their final [tex] \omega [/tex] and calculate the initial and final energies.
 

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