(adsbygoogle = window.adsbygoogle || []).push({}); Pivot point on a Uniform Rod and Acceleration

I'm stuck on this question, which seems like it should be fairly simple:

A uniform rod of length 1.15 m is attached to a frictionless pivot at one end. It is released from rest from an angle theta = 21.0° above the horizontal. Find the magnitude of the initial acceleration of the rod's CM.

theres a graphic of it here:

http://capaserv.physics.mun.ca/msuphysicslib/Graphics/Gtype20/prob28_1012rod.gif

ok so what I've done so far is:

Rmg(sinθ) = Iα

Rmg(sinθ) = (1/3)mL^2α

getting the expression I = (1/3)mL^2 from my text book for a uniform rod with a pivot at its end.

working that out I get:

(0.575)(9.8)(sin21) = (1/3)(1.15)^2 α

α = 4.58 rad/s

then converting α to a with:

a = Rα

a = (.575)(4.58)

a = 2.63 m/s^2

but apparently this isn't right.

can anyone help me out?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Rotational moments of Inertia

**Physics Forums | Science Articles, Homework Help, Discussion**