Oscillations and damping (air resistance)

[tom12345]

If anyone could help with the following, it would be great.

I am currently carrying out an experiment for a school project to see how damping affects and reduces the amplitude of the oscillation of a pendulum. For the pendulum I am using a suspended metre ruler and I will count the number of oscillations before the ruler does not reach a certain amplitude anymore. To vary the level of damping, I am going to attach different surface areas of cardboard to the ruler and then plot a graph of surface area of cardboard (x-axis) verses the oscillation number (y-axis). Having just done this, I get what looks like an exponential decay relationship. Any suggestions or information on why this would be? Thanks.

 

[arunma]

Air resistance is directly proportional to surface area. So if you double your surface area, you'll double the air resistance.

It's also important to remember that amplitude decreases continuously and not discretely. Every oscillation will decrease the pendulum's amplitude. So it might be a good idea to record the amplitude of every oscillation of your pendulum

 

[Mentz114]

The oscillations of a damped oscillator do decay exponentially. But you're measuring something like the accumulated decay over a number of swings.

Try plotting 1/n or log(n) against area.

Have look at the damped oscillator in Wikipedia.