# Homework Help: SHM of a pendulum

1. May 1, 2014

### LunaTech

1. The problem statement, all variables and given/known data
A uniform steel bar swings from a pivot at one end with a period of 1.2 seconds. How long is the bar?

2. Relevant equations
T=2$\pi$$\sqrt{L/g}$

3. The attempt at a solution
I manipulated this equation to solve for L, giving me L=$T^{2}g/4\pi^{2}$
Plugged in T=1.2 seconds and g=9.8. Answer I got was (to two significant figures) 0.36 m. But apparently that answer is wrong so I don't know what I am missing or if I am using the wrong equation.

2. May 1, 2014

### Staff: Mentor

The equation you are using is for a simple pendulum, where all the mass is concentrated at the end. When the mass is spread out, as in your problem, you have what is called a physical pendulum, so you'll need to modify that formula a bit. Read this: Physical Pendulum

3. May 1, 2014

### LunaTech

That clears things up a bit. I got the answer now. Thanks.