# Angular Momentum tricky problem

1. Oct 20, 2013

### lecammm

1. The problem statement, all variables and given/known data
As the picture shows, we are given several variables, but I am near completely lost. I am behind in my course and am trying to catch up as best as I can but this problem is really hard for me

2. Relevant equations

The equations that I have used are;

parallel axis theorem

3. The attempt at a solution
I know that this solution will be completely wrong as I haven't utilised the frictional torque, nor the angle.

So, by applying the parallel axis theorem for the mass moment of inertia;

I0 = I + mr^2
I(slender bar) = 1/12 * m * L^2
∴ I0 = 1/12 * m * L^2 + mr^2

then used the fact that:

ƩM0 = I0:

and therefore:

mgb = I0 * angular acceleration:
where b is the distance from the COM

however, as assumed, this gave the wrong answer, I'm really stuck with it and I want to know how I can do it for problems to come. Thanks!! :D
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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2. Oct 20, 2013

### SteamKing

Staff Emeritus
You need to show your calculations.

Your equation for the sum of the moments = I0 is incomplete.

How are we to know what you've done if you don't provide your work?