# Angular acceleration of a pulley

1. Nov 8, 2009

### ryty

1. The problem statement, all variables and given/known data
A 2.70 kg bucket is attached to a disk-shaped pulley of radius 0.141 m and mass 0.792 kg. If the bucket is allowed to fall,
A- What is linear acceleration?
B- What is angular acceleration?
C- How far does the bucket drop in 1.5 s?

2. Relevant equations
a=g/(1+ (I/mr^2))
alpha=delta w/delta t

3. The attempt at a solution
i tried using both equations for a and b, but they both came up wrong

2. Nov 8, 2009

3. Nov 8, 2009

### ryty

9.8/(1+(2.7*.141^2)=4.9
but this didnt work for either answer, and i dont know how to get time out of this, so im not real sure if you can use the second equation

4. Nov 8, 2009

### rl.bhat

(2.7*.141^2) This is only M*R^2. Bur in the relevant equation you need
I/mr^2, where I is the moment of inertia of the pulley. Find this value.

5. Nov 8, 2009

### ryty

what about gravity, should i still use my original equation?

6. Nov 8, 2009

### rl.bhat

After substituting the value of I, the acceleration a is
a = g/( 1 + M/2m)

7. Nov 8, 2009

### ryty

which m is which mass, is M the mass of the bucket, pulley or both? and is m the mass of the bucket, pulley or both?

8. Nov 8, 2009

### rl.bhat

M is the mass of the pulley, because I is the moment of inertia of the pulley.