Posted by Bruce on Friday, July 20, 2012 at 10:32am.
A uniform brass disk of radius R and mass M with a moment of inertia I about its cylindrical axis of symmetry is at a temperature T = 45 °C. Determine the fractional change in its moment of inertia if it is heated to a temperature of 125 °C. (The linear expansion coefficient for brass is 1.90 105 °C−1.)
I tried finding the change in volume and using that ratio, but it isn't correct. Im not sure what the best approach is. Thank you for any suggestions!

physics  ajayb, Friday, July 20, 2012 at 12:02pm
You have been given the linear expansion coefficient  find increase in radius R and then find the disk's MI.

physics  Elena, Friday, July 20, 2012 at 2:37pm
ΔR=R•α•ΔT=R•1.9•10^5•(12545)=0.00152•R
R1=R+0.00152•R =R•1.001525
I=mR²/2
I1= mR1²/2= mR²•1.001525²/2=1.003• mR²/2=1.003•I
I1/I=1.003 or
I/I1=1/1.003=0.997

physics  Bruce, Monday, July 23, 2012 at 11:09pm
thank you!
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