# Homework Help: Rotational Kinematics of a CD

1. Apr 4, 2006

### Huskies213

Can anyone help me with these 2 ?

1.) A cd with a diameter of 12 cm, speeds up from 0 to 4 rev/s in 3s. What is the tangential acceleration of a point on the outer rim of the disk at the moment when angular speed is a.) 2 rev/s b.) 3 rev/s

2.) A fisherman reels in a fish and turns the spool on the reel at a rate of 3 revolutions per second. If the radius of the reel is 3.7 cm, what is the linear speed of the fishing line as it is reeled in ?

2. Apr 4, 2006

### Pengwuino

You need to show some work before we can help.

3. Apr 5, 2006

### Axelerator

remember to get frequency its 1/t, so convert it the rev/s to Hz. I hope i'm correct?

4. Apr 8, 2006

### Huskies213

Re

I don't know where to start .. can anyone Help ?

5. Apr 8, 2006

### Hootenanny

Staff Emeritus
A formula for tangental acceleration is;

$$\alpha = \frac{a_{t}}{r}$$

where $\alpha$ is angular acceleration and $a_{t}$ is tangental acceleration.

-Hoot