Calculating Force of Falling Weight in Closed System

[jesuslovesu]

I'm just wondering if I'm doing this correctly..

If I have something like this: http://img326.imageshack.us/my.php?image=pull6cx.png

It's a closed system where the weights on the cart will get placed on the bottom holder for each trial... To find the 'force of the falling weight' I would take the mass*acceleration, where acceleration is determined by how fast the cart goes in a certain distance right? I wouldn't just take the mass*gravity when it's connected to a pulley like that would I?

 

[Erwin Schrodinger]

The only forces acting on the falling weight are Fg1 (force of gravity) and FT (force of tension in the rope). For the falling weight alone, Fnet1 = ma = Fg1+FT.

Since FT is applied in both directions in the rope, it "cancels out" when you involve the entire system. For the entire system, Fnet = (m1+m2)a = Fg1+Ff2.

Hope that helps.