Terminal Speed of 6.5 kg Ball: Calc Error?

[GingerBread27]

What is the terminal speed of a 6.5 kg spherical ball with a radius of 3.0 cm and a drag coefficient of 1.50? The density of the air through which the ball falls is 1.2 kg/m3.

I used vt=sqrt((2Fg)/(CpA)). Where Fg is force of gravity, C is drag coeff., p is air density , and A is cross sectional area. When I plug in the numbers I get the wrong answer. I used 1.5 as C, 1.2 as p, 9.8 as Fg, and (9*pi) as a (area of circle-pi*r^2). What am I doing wrong.

 

[freddy]

I think you need to convert your radius to meters.

 

[GingerBread27]

I forgot to convert lol but that doesn't help, answer is still wrong.

 

[GingerBread27]

Never Mind Figured it Out :)

 

[Clausius2]

Your expression hasn't got units of velocity.

I think you have forgotten to include the sphere mass in Fg.