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Terminal Speed

  • #1
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.
 

Answers and Replies

  • #2
freddy
I think you need to convert your radius to meters.
 
  • #3
I forgot to convert lol but that doesn't help, answer is still wrong.
 
  • #4
Never Mind Figured it Out :)
 
  • #5
Clausius2
Science Advisor
Gold Member
1,435
5
Your expression hasn't got units of velocity.

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

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