# A drag force question

1. Oct 4, 2005

### azure.hubris

The first part of a pretty involved, 8 part question on modelling drag force states: "A 0.142 kg ball has a terminal speed of 42.5 m/s. If a ball experiences a drag force of R=CV^2, what is the value of the constant, C?

I know this is a ridiculusly easy problem, but our text doesn't cover the formula for drag force at all, and I'm not sure what the R variable is. I mean, I know that v is velocity, so you'd think by elimination, R must be somehow represent mass, but the answer that produces isn't accepted by the homework system. So, who wants to tell me what R is, and possibly make fun of my ignorance a little too? Any takers?

2. Oct 4, 2005

### CarlB

Use F = ma = drag force, with the left side determined by gravity's force, and the right side given by the drag force.

Don't worry about it being ridiculously easy. If that's your worst problem this semester you done good.

Carl

3. Oct 4, 2005

### James R

The question tells you "a drag force of R=..."

That is, R is a force - a drag force.

4. Oct 4, 2005

### azure.hubris

Okay, I see. Thanks for the assistance.