# Centripetal Acceleration circular disk

1. May 31, 2009

### Simple Echo

1. The problem statement, all variables and given/known data
A circular disk of radius 30 cm is rotating with an angular acceleration of 1 radian/ s2. What is the tangential acceleration of a point on the rim of the disk? What is its centripetal acceleration if the angular speed is 3 rev / s?

2. Relevant equations
tangential acceleration = angular acceleration * radius

3. The attempt at a solution
tangential acceleration = 1 * 30 = 30 cm/sec^2

I'm not even sure I got that part right, my online reading just throws a bunch of random variables at me, and I have no idea what they're referring to. If someone could just explain the equation to me to figure out the Centripetal Acceleration, that would be great. I'm not asking you to do it, I just want to know how. I already failed at this question.

2. May 31, 2009

### rock.freak667

What formula did you use for centripetal acceleration?

3. May 31, 2009

### Simple Echo

That's one of my problems, I have no idea what the formula is to use.

4. May 31, 2009

### Simple Echo

ac = v^2/r

So
Centripetal Acceleration = 3^2/30?
0.3 rev/s

I don't even think this is the right equation

5. May 31, 2009

### rock.freak667

$$a_c=\frac{v^2}{r}$$

but remember that v=rw so substitute that to get another form of centripetal acceleration.

6. May 31, 2009