How does a balanced pulley system move if it's in equilibrium?

[Seneka]

Homework Statement

2. Relevant equation

The Attempt at a Solution

...[/B]
Part c)
I'm confused as to how the actual pulley system works. If its balanced wouldn't it be stationary. How does it move?
I thought that since its balanced the acceleration of the system is constant and therefore to find the average kinetic energy of the system, I would just do 1/2 x (2000 + 1000) x (9/30)^2
The answers say that the weight only moves half as far. How do you know this?

 

[Doc Al]

If its balanced wouldn't it be stationary. How does it move?

I believe by "balanced" they mean that the net force is zero.

The answers say that the weight only moves half as far. How do you know this?

Note how the cable attaches to the weight. When the weight moves down by 1 unit, how much cable must move through the pulley above the car? (You might want to play around with a piece of string to better visualize what happens.)