# Rotational motion

1. Jun 12, 2005

### john_halcomb

have a question.
diameter of a rotor is 7.60m and rotational speed of 450 rev/min. calculate speed of tip. anywell would be welcomed

2. Jun 12, 2005

### Pyrrhus

What equation relates both?

$$v = \omega r$$

3. Jun 12, 2005

### john_halcomb

the answer in the back of the book says179 m/s. but when i try that formula it comes out as 311.6

4. Jun 12, 2005

### Pyrrhus

Oh sorry, yes the book is right

A rev is equal to 2 pi radians, and a minute is equal to 60 second. You need to homogenize (spl?) your units.

5. Jun 12, 2005

### john_halcomb

the rev/min is 47.81 rev/sec

6. Jun 12, 2005