How Do You Calculate Angular Acceleration of a Disk?

[jonnyboy]

[SOLVED] Angular acceleration of disk

For the system below, determine the tension in each rope, the linear acceleration of each mass and the angular acceleration of the disk. \ g=10 m/s^2. Use \ I=4 kgm^2.

So far I have drawn the free-body diagram for m1 and m2
\ 120 - T_1 = 12a_1 and \ T_2 - 40 = 4a_2
and have figured \ T_1 - 2T_2 = 4\alpha
\ a_2 = 2\alpha
\ a_1 = \alpha

 

[Doc Al]

So far I have drawn the free-body diagram for m1 and m2
\ 120 - T_1 = 12a_1 and \ T_2 - 40 = 4a_2
and have figured \ T_1 - 2T_2 = 4\alpha

So far, so good!

\ a_2 = 2\alpha
\ a_1 = \alpha

Excellent. Now use this to rewrite a_1 and a_2 in terms of \alpha in your first two equations. Then you'll have three equations and three unknowns, which you can solve.

 

[jonnyboy]

Thanks. I've got it from there. Just didn't realize how easy it was once I had that.