# Angular Acceleration (and other torque/angular problems)

**1. The problem statement, all variables and given/known data**

A thin, uniform stick of length 2.1 m and mass 3.9 kg is pinned through one end and is free to rotate. The stick is initially hanging vertically and at rest. You then rotate the stick so that you are holding it horizontally. You release the stick from that horizontal position. What is the magnitude of the angular acceleration of the stick when it has traveled 25.6 degrees (the stick makes an angle of 25.6 degrees with the horizontal)?

**2. Relevant equations**

Inertia = (1/3)mL^2

T=I(alpha)

T=Frsin(ø)

**3. The attempt at a solution**

T=mgrsin(ø)

T=3.9*9.81*(2.1/2)*sin(25.6)=17.36

I=(1/3)3.9*(2.1^2)=5.733

T/I=17.36/5.733=3.03 rad/s/s

That’s not correct . . . there’s a lot more problems too that I’m not getting and I have no clue why, but I want to start here first.

http://ift.tt/1bTptoj

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