# Homework Help: General physics

1. Sep 20, 2007

### Littlemstrouble

1. The problem statement, all variables and given/known data
A pulley is a uniform cylindrical disk of mass m and radius r. The strings are massless and there is no friction. If the system is initially at rest, find the speed of the blocks (m1 and m2) after they have moved a distance d.

m1----------0
**********l
**********l
**********l
**********m2

2. Relevant equations

3. The attempt at a solution
The answere should be v = square root(4gd/5)
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Sep 20, 2007

### Dick

You'll need to look at the change in the gravitational potential energy of m1 and m2 and equate that to the kinetic energy of m1 and m2 plus the rotational kinetic energy of the disk. I don't believe your answer unless there is a special relation between m1, m2 and m.

3. Sep 21, 2007

### chaoseverlasting

If there is no friction, then tension in the string is constant and the speed of m1=m2. Now, v(m1)=v(m2)=rw where r is the radius of the disk and w is the angular velocity.