# Homework Help: Two masses suspended from a pulley

1. Aug 10, 2009

### rusticle

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

hi, Im really stuck on this question:

Two masses m and M, M>m are joined by a massless inelastic string and suspended from a pulley of radius R and moment of inertia I. the pulley rotates about its centre freely with no friction. The system starts at t=0 from rest. during the motion of the system, the string does not slip on the pulley's rim.

2. Relevant equations

a) Find the acceleration of M. What sort of motion is produced?
b)Are the tensions on each side of the pulley the same? Do they vary with time? Find thier magnitude(s) in terms of M, m, I and g.

3. The attempt at a solution

i have produced a free body diagram and come up with the following equations:

ma + Ma = mg + Mg - [T][/m] - [T][/M] (1)

Newton II (rotational ver) I(alpha) = TR (2)

and a = R(alpha)

im not sure where to go next, or if im correct with these equations.
help would be muchly appreciated

#### Attached Files:

• ###### pulley system.doc
File size:
27 KB
Views:
117
2. Aug 10, 2009

### Staff: Mentor

Your equations (1) and (2) are not quite right. Show how you got them. (I suggest writing a separate equation for each mass, so you end up with three equations.)