# Angular velocity of airplane propeller

1. Mar 13, 2004

### lollypop

here is the problem:
An airplane propeller is 2.08 m in length (from tip to tip) and
has a mass of 117 kg. When the airplane's engine is first started,
it applies a constant torque of 1950 N*m to the propeller, which starts from rest.
-What is the angular acceleration of the propeller? Treat the propeller as a slender rod.
For this part i got 46.23 rad/s^2 finding first I=(1/12)ML^2
and then plugging that into acc angular = torque/I

What is the propeller's angular speed after making 5.00 rev?
-for this part i get confused, am i supposed to use
5 rev "per min". i used the formula v = w*r where
w= 2*pi*frequency, but it is not right.
can anyone direct me to the right formula??
thanks.

2. Mar 13, 2004

### Janitor

Hint

Remember the problems you have solved with constant linear acceleration g? In that case, if you were asked how fast an object was moving after it had gone a certain distance, you would first use the fact that x=(1/2)gt^2 (if initial position is zero and initial velocity is zero) to solve for t, given some position x. Then you would substitute that value of t into v=gt, and you would have your answer.

The angular acceleration procedure is very much analogous.