Pivoting Cylinder Homework: Find Angular Acceleration

[gonzalo12345]

Homework Statement

M, a solid cylinder (M=1.63 kg, R=0.119 m) pivots on a thin, fixed, frictionless bearing. A string wrapped around the cylinder with a mass m = 0.830 kg is hung from the string, find the angular acceleration of the cylinder.

http://lc2.mines.edu/res/msu/physicslib/msuphysicslib/20_Rot2_E_Trq_Accel/graphics/prob16b_002masspulley2.gif

Homework Equations

torque = I(alpaha)

The Attempt at a Solution

I tried to solve the problem algebraically, and got (2mR)/(MR^2 - 2mR^2) but I keep getting it wrong.

 

[tiny-tim]

I tried to solve the problem algebraically, and got (2mR)/(MR^2 - 2mR^2) but I keep getting it wrong.

Show us what you tried, and then we'll be able to see where the mistake was.