# Homework Help: Rotational Velocity and Acceleration

1. Apr 8, 2012

### PhysicsScrub

1. Electric toothbrushes can be effective in removing dental plaque. One model consists of a head 1.1 cm in diameter that rotates back and forth through a 70.0 angle 7600 times per minute. The rim of the head contains a thin row of bristles. (See the figure )Assuming that the toothbrush has constant angular acceleration in each of the directions it turns, find the angular acceleration (in rad/sec2 ) of the rotating head and the tangential acceleration (in m/s2 ) of the bristles.

What is the rotational acceleration in rad/sec2

What is tangental accelration in m/s2

Last edited: Apr 8, 2012
2. Apr 8, 2012

### Staff: Mentor

Seriously? A toothbrush 1.1 inches in diameter? :surprised Is it for horses?

3. Apr 8, 2012

### PhysicsScrub

Oops. that should say 1.1 cm

4. Apr 8, 2012

### Staff: Mentor

Phew! You had me worried for a moment there

So assuming that the brush goes from zero to angle seventy degrees in a half period, what is the required angular acceleration?

5. Apr 8, 2012

### PhysicsScrub

realllly unsure bud

6. Apr 8, 2012

### Staff: Mentor

Well, if it goes back and forth 7600 times every minute, what's the period for one cycle?