Angluar Velocity and Revolutions

[Jar9284]

Homework Statement

You switch a food blender from its high to its low setting; the blade speed drops from 3100 rpm to 1300 rpm in 2.1 s. How many revolutions does it make during this time?

Homework Equations

\omegai = \frac{3100 rpm * (2 * pi)}{60} = 324.6 rad/sec
\omegaf = \frac{1300 rpm * (2 * pi)}{60} = 136.1 rad/sec

\omegaf = \omegai + \alphat

\omegaf^{2} = \omegai^{2} + 2\alpha(\Delta\Theta)

The Attempt at a Solution

136.1 = 324.6 + 2.1 \alpha

\alpha = 89.8 rad/sec^{2}

136.1^{2} = 324.4^{2} + 2 * 89 (\Delta\Theta)

(\Delta\Theta) = 482.8 rad / (2 * pi) = 76.8 rev

Want to make sure if this is correct.

 

[mezarashi]

Looks good to me :)