# Spinning Disk problem. Due tomorrow! Help please

1. Sep 8, 2008

### rgalvan2

Spinning Disk problem. Due tomorrow! Help please!!

A disk with a diameter of 0.1 m is spinning about an axle perpendicular to the disk and running through its center.
a) How many revolutions per second would it have to rotate in order that the acceleration of the outer edge of the disk be 14 g's (i.e., 14 times the gravitational acceleration g)?

b) For the frequency determined in part (a), what is the speed of a point half way between the axis of rotation and the edge of the disk?

c) At this same frequency, what is the period of rotation of this "halfway point"?

d) How long does it take a point on the edge of the disk to travel 1 km?

I got questions a) which is 8.3 seconds.
I am stuck on b). I tried v=$$\omega$$R. I also converted 8.3rev/s back to rpm which was 498rpm. So v=498rpm(.025m)=12.45meters/min. My answer needs to be in m/s so I divided by 60 and got .2075. It's not right. What am I doing wrong?

2. Sep 8, 2008

### rgalvan2

Re: Spinning Disk problem. Due tomorrow! Help please!!

Never mind I got it! :)