# Oscillating mass

1. Nov 7, 2004

### dg_5021

simple pendulm

If I suspend a baseball bat from one end and let it swing back and forth does it make a simple pendulm?

2. Nov 7, 2004

### dg_5021

Under what conditions does an oscillating mass tied to a string constitute a simple pendulum?

3. Nov 7, 2004

### Integral

Staff Emeritus
Please show us that you have but some thought of your own into these questions.

4. Nov 7, 2004

### dg_5021

I know that a simple pendulum consists of a mass m tied to a string (considered massless) of length L. So If I suspend a baseball bat from one end and let it swing back and forth does it make a simple pendulm

5. Nov 7, 2004

### Pyrrhus

No, it will make a physical pendulum.

6. Nov 7, 2004

### dg_5021

Under what conditions does an oscillating mass tied to a string constitute a simple pendulum?

7. Nov 7, 2004

### Pyrrhus

When it's point-mass ($I_{cm} = mr^2$) tied to the massless string.

Try it:

Physical pendulum Period

$$T = 2 \pi \sqrt{\frac{I}{mgd}}$$

Substituting for ($I_{cm} = mr^2$)

$$T = 2 \pi \sqrt{\frac{mr^2}{mgd}}$$

$d = l = r$

$$T = 2 \pi \sqrt{\frac{l}{g}}$$