Damping constant.

[NINHARDCOREFAN]

How do I find the damping constant of a pendulum? Is there a formula?

[berkeman]

I'd assume that you start with the equations of motion for an undamped pendulum, and then add in a retarding force that increases with angular velocity. Are you familiar with how to derive the equation of motion of a pendulum from the length and the mass?

[NINHARDCOREFAN]

No, all I know is how to find its period.

[tim_lou]

you need to work with linear differiential equations. you can have linear drag or quadratic drag (then it will be nonlinear). i suggest you learn some projectiles motions involving air resistance first if all you know is the formula for the period....

[NINHARDCOREFAN]

Can someone please give me the equation with length and mass? I'll try to derive it.

[berkeman]

Can someone please give me the equation with length and mass? I'll try to derive it.
We don't give out answers here in the PF. We guide:

http://en.wikipedia.org/wiki/Pendulum