# Centripetal Force acceleration

1. Jan 27, 2009

### luap12

1. A computer is reading data from a rotating CD-ROM. At a point that is 0.0330 m from the center of the disk, the centripetal acceleration is 264 m/s2. What is the centripetal acceleration at a point that is 0.0702 m from the center of the disc?

2. ac=v2/r

3. So my thoughts here are that it should be assumed that the velocity is constant. So I need to fine that velocity for the known radius and acceleration with the equation about. After I find the velocity, I can plug it into the equation with the new radius and find the acceleration that way.
ac=v2/r
264=v2/.0330
v2=8.712 m/s
v=2.95161 m/s

then plugging that into the equation with the other radius
ac=v2/r
ac=8.712/.0702
ac=124.10256 m/s2

This is not the right answer for my homework though. Not sure what I am doing wrong. Anyone know?

2. Jan 27, 2009

### praharmitra

well...the disc is rotating...so v is NOT constant. However, for constant rotation, angular velocity is constant. Use the relation between that and v, and modify your equation for acceleration.

3. Jan 27, 2009

### luap12

ok, I understand now that the velocity is not constant. I don't believe we have covered angular velocity yet in class, unless I am just overlooking it. How do you do that? I did set up a proportion though with the velocity and radius and got it correct.

4. Jan 27, 2009