# Rotational motion

#### 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

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#### Pyrrhus

Homework Helper
What equation relates both?

$$v = \omega r$$

#### 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

#### Pyrrhus

Homework Helper
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.

#### john_halcomb

the rev/min is 47.81 rev/sec

#### Pyrrhus

Homework Helper
Multiply it with 3.8 m

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