# Homework Help: Calculating Air Resistance

1. Nov 16, 2012

### jff0404

1. After dropping coffee filters, I have to derive or describe the relationships between air Resistance(R) and v or v^2, whichever is right, and draw a graph. I can find derivations on internet as long as I site.
I have time, v, height and acceleration, but no reference area. All the equations I've seen need the ra, is there any way I can find R without it?

2. v=m/s
a= v/s = m/s^2
Net F = R-w
w=mg
D = Cd * r * V^2 * A/2

3. When the object reaches terminal v, a=0. So I put 0 for a= (W - D)/m that I also got from the internet, but I got something useless with m/s units(supposed to be in N because R is a force). I don't know what I'm supposed to do!

2. Nov 16, 2012

### CWatters

Rearrange..

0 = (W - D)/m

to give..

W = D

You can measure W.

Plot V or V2 against W (=D) and see what you get.

3. Nov 16, 2012

### CWatters

PS Try to ensure the filters stay the same shape as they fall, eg don't add too much weight.