(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A uniform rod of length 0.750 m and mass 1.20 kg is pivoted at one end by a smooth pin as shown below. The rod is released from the vertical position and given a slight nudge to release it from the vertical position of unstable equilibrium.

[PLAIN]http://img175.imageshack.us/img175/9820/angacc40pc.png [Broken]

When the rod is horizontal:

(a)Calculate its angular acceleration.

(b)Calculate the x and the y components of the acceleration of the centre of mass.

3. The attempt at a solution

First I focus on part(a). I have already obtained the angular velocity:

The potential energy of the system relative to the reference configuration is MgL/2 because the center of mass of the rod is at a height L/2 away from its position in the reference configuration. Conservation of mechanical energy for the system is:

K_{i}+U_{i}= K_{f}+ U_{f}

0+½MgL=½Iω²+0

[tex]\omega = \sqrt{\frac{MgL}{\frac{1}{3}ML^2}} = \sqrt{\frac{3g}{L}}[/tex]

using the given values I get ω=6.26 rad/s, which is the correct velocity.

Now I want to use the equation [tex]\alpha = \frac{\Delta \omega}{t}[/tex] to find the angular acceleration. Here's where I'm stuck. Could anyone please show me how to find the time for this equation?

Correct answer to part (a) is 19.62 rad/s² and for part (b) it is -14.7 m/s²(x-component) and -7.36 m/s² (y-component)

**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: Angular Motion

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