# Dampening effect on a pendulum

1. Apr 17, 2010

### BEEFCOPTER

Ok, my mind has gone blank. What equation do I use to calculate the time a pendulum will take to come to a complete stop?.. I have all variables, length of string, angle it was released, etc.. I know the equation for period, but how do I figure how long till it stops from DAMPENING effect..?

This isn't really a homework question, its just for something I am building. So hopefully this is the right place to post. Thanks!

2. Apr 17, 2010

### kandyfloss

I guess you use the time period formula for pendulum
T=2pie.sqrt(L/g)

3. Apr 17, 2010

### twang

That would vary from pendulum to pendulum... there's no way to calculate how long it keep swinging without knowing the sources of friction. There's friction 1. in the bearing of the pendulum's pivot point (unless its a wire tied to a point, in which case there's energy lost in the wire) 2. between the surface of the pendulum's weight or 'bob' and any gas or liquid it's swinging in.

Once you know that damping force (experiment) you can use the equation here: http://en.wikipedia.org/wiki/Pendulum

4. Apr 17, 2010

### BEEFCOPTER

Ok, so, forgive me if these questions are remedial, physics is not my strongest subject. So: If, knowing the total coeffeicient of friction (of the pivot point, as well as the air resistance) what equation would represent total time until the pendulum comes to rest?