# Disk acceleration physics homework

1. Nov 13, 2009

### monkey9988

1. The problem statement, all variables and given/known data

A force of 2.2N acts tangentially to the rim of a solid 52kg disk, with a radius of 32cm. How long does it take to accelerate the disk, rotating about an axis though it's center and perpendicular to it's plane, from rest to 210 rev/min?

2. Relevant equations
Idisk=.5mr^2
T=I (wierd fish symbol)
fish symbol = Wf - Wi
t

3. The attempt at a solution
i dont know how to find the wierd fish symbol.. one because i dont know what it stands for and two. i need that inorder to find time..

2. Nov 13, 2009

### Andrew Mason

Welcome to PF.

The wierd fish symbol is the greek letter alpha: $\alpha$ which means angular acceleration and has units of radians/time^2. The relationship between acceleration (distance/time^2) and $\alpha$ for a point rotating about a centre of rotation located at a distance r away is: $\alpha = a/r$.

The relationship between torque and angular acceleration for a rigid object is:

$$\tau = I\alpha$$

In order to answer this question, you will have to understand what that equation means.

AM