## Revolutions per minute

1. The problem statement, all variables and given/known data

An electric-generator turbine spins at 3460.0 rpm. Friction is so small that it takes the turbine 14.9 min to coast to a stop. How many revolutions does it make while stopping? (Do not include a unit with your answer.)

2. Relevant equations

rev/min * 1min/60sec = rev/sec
T (period) = 1/(rev/sec)
w (omega) = 2pi/T
wf = wi + at/r *delta t where at is tangential acceleration and r is radius

3. The attempt at a solution

346.0rev/min * 1min/60sec = 57.66 rev/sec

T = 1/57.66 = 0.0173 seconds

w = 2pi/T = 2pi/0.0173 sec = 363 rad/sec

So I did all the above, but to solve for tangential acceleration I need a radius, which is not given in the question. Once I find tangential acceleration, I can substitute it into the following equation:

Theta final = Theta initial + wi * delta t + ar/2r (delta t ^2)

and theta final can be converted into the number of revolutions.

This is a non-uniform circular motion question.

Tina
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
 PhysOrg.com science news on PhysOrg.com >> King Richard III found in 'untidy lozenge-shaped grave'>> Google Drive sports new view and scan enhancements>> Researcher admits mistakes in stem cell study
 Recognitions: Gold Member Science Advisor Staff Emeritus I think you can use a considerably simpler rotational equation than the one your propose. http://hyperphysics.phy-astr.gsu.edu...rotq.html#drot

 Tags non-circular motion, rpm, tangential a