# Homework Help: Find the value of aerodynamic constant C for this dimpled sphere.

1. Feb 27, 2013

### Sneakatone

A falling golf ball (mass 45 g, radius 20.0mm) reaches high terminal speed of 42 m/s. what is the value of the aerodynamic constant C for this dimpled sphere?

I tried using mv^2/r -> (0.45 kg)*(42 m/s)/0.2m=94.5 but Its not correct. I dont understand what they mean by constant C.

2. Feb 27, 2013

### SteamKing

Staff Emeritus
Well, the golf ball is undergoing linear motion. Your formula is for the centripetal force on an object in circular motion. What you need is a formula for terminal speed of an object which is falling.

3. Feb 27, 2013

### Sneakatone

V=sqrt(2mg/pAC)

4. Mar 1, 2013

### Sneakatone

if this is the right equation should the units of v=km/h and r=m?
in other words what should the units be?

5. Mar 1, 2013

### haruspex

Anything you like as long as you are consistent. Put everything into MKS units and you should be safe.

6. Mar 1, 2013

### Sneakatone

would you recomend I convert to km since p is km?

Last edited: Mar 1, 2013
7. Mar 1, 2013

### haruspex

Isn't p (rho) the density? That would be kg/m3 in MKS.