How Do You Calculate Angular Acceleration in a Pivoting Rod Problem?

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Homework Statement


A uniform horizontal rod of mass 2.8 kg and
length 2.1 m is free to pivot about one end
as shown. The moment of inertia of the rod
about an axis perpendicular to the rod and
through the center of mass is given by I =(m ℓ^2) /12

If a 4.8 N force at an angle of 63◦
to the horizontal acts on the rod as shown, what is the
magnitude of the resulting angular acceleration about the pivot point? The acceleration
of gravity is 9.8 m/s^2
.
Answer in units of rad/s^2


Homework Equations


Sum of the torques = I * a
Torque = R * F * sin(theta)

The Attempt at a Solution



Here is what I have so far:

(sum of the torques) = (Torque of force F)
I * a = R * F * sin(63)
a = (R * F * sin(63)) / I

I = (M * L^2)/3 (It is rotating at its endpoint not at its center of mass)

a = (3 *(R * F * sin(63))) / (M * L^2)
a = (3 *(2.1 * 4.8 * sin(63))) / (2.8 * 2.1^2)
a = 2.1821 rad/s^2 <-----But this answer is incorrect. Where did I go wrong?

 
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Sorry if you came to this but I just figured it out. I forgot the torque due to gravity
 
To solve this, I first used the units to work out that a= m* a/m, i.e. t=z/λ. This would allow you to determine the time duration within an interval section by section and then add this to the previous ones to obtain the age of the respective layer. However, this would require a constant thickness per year for each interval. However, since this is most likely not the case, my next consideration was that the age must be the integral of a 1/λ(z) function, which I cannot model.
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