# How to find g using a simple pendulum?

1. Sep 5, 2009

### xXsKiLLzXx

How to find "g" using a simple pendulum?

We just started physics in grade 11.
I have no idea of how to find g using a pendulum.
This a lab we will have to do soon in the near future
I am here to do some research before we have to do the lab.
I've done some other research on the net, and i came up with no solution.

What is the equation for to determine g from a pendulum?
What are the variables?
Thank you!

2. Sep 5, 2009

### Nabeshin

Re: How to find "g" using a simple pendulum?

Perhaps you could try researching the general phenomenon of simple harmonic motion first, leading to the specific case of a pendulum.

3. Sep 5, 2009

### RoyalCat

Re: How to find "g" using a simple pendulum?

What you'll most likely be doing is measuring the period of the pendulum (How long it takes for it to complete one swing back and forth.)

Explore the general case of simple harmonic motion to find the formula for the period of such a motion, and then see what the period is for a mathematical pendulum (The kind you'll be exploring in your lab.)

Just to give you a biiiiig hint, at some point during your work, you'll see that for a swinging pendulum, simple harmonic motion does not hold. However, at small angles, $$\theta\approx\sin{\theta}$$ holds true, so you can use it to describe the motion of the pendulum as simple harmonic.

4. Sep 5, 2009

### Hurkyl

Staff Emeritus
Re: How to find "g" using a simple pendulum?

I think you may be thinking about the problem backwards.

A formula that takes information about a pendulum and gives you the value of g would work, sure.

But wouldn't about a formula that takes g and tells you information about the pendulum work just as well?

5. Sep 6, 2009

### PrincePhoenix

Re: How to find "g" using a simple pendulum?

We did that.
Time period T = 2(pi)*under root of (length of pendulum/g).
(pi=3.14)
You find value of time period and length of pendulum. Then modify the above equation,put the values and calculate.