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Solve rpm in rotational motion problem

  • Thread starter adca14
  • Start date
11
0
1. Homework Statement
How fast (in rpm) must a centrifuge rotate if a particle 7.0 cm from the axis of rotation is to experience an acceleration of 100,000 g's?

My variables
radius= 7 cm or .07m
radial accel= 100,000 g's or 980,000m/s^2 or 98,000,000cm/s^2
V= I think I need this to get w
w= ? I think I need to solve this to get rpm
rpm= ? this is what I want


2. Homework Equations
radial accel = v^2/r
v= rw


3. The Attempt at a Solution
980000/.07 = 68,600


[tex]\sqrt{}68600[/tex]/.07= 261.9
261.9/.07 = 3,741 rpm

whether i set everything as meter or centimeter, I still get the same answer. I check the back of the book and it says 3.6x10^4 or 36,000rpm
1. Homework Statement


Any help would be appreciated.
 

Answers and Replies

Dick
Science Advisor
Homework Helper
26,258
618
Your answer is correct but it's in radians per second. rpm is revolutions per minute. A revolution is 2*pi radians and a minute is 60 seconds. Can you convert it to rpm?
 
11
0
thank you, I did:
3741rad*60=224,460
224,460/2*pi=35,723rpm or 36000rpm if I round up. Thanks again!
 

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