How Do You Find g Using Atwood's Machine?

[blindsided]

Hi!
I have an assignment to write a mini-essay of sorts on Atwood's machine. One of the things I need to cover is how to find the value of g by using Atwood's machine. I really have no idea how to do this. I was thinking about rearranging a= [(m₂-m₁)g] / (m₁+m₂) but I don't understand how to get a.
Help would be greatly appreciated!

 

[Doc Al]

... but I don't understand how to get a.

If you are using this to find g, you'd have to measure the acceleration.

 

[blindsided]

Ah, I understand now. Thank you!