# Is this in equilibrium?

1. Aug 9, 2010

### CountFleet

Are these two boxes in equilibrium?

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2. Aug 9, 2010

### Staff: Mentor

What is the context of the question? Is it for a class? What do you think?

3. Aug 9, 2010

### CountFleet

I'm not taking a physics class right now. I'm just trying to learn on my own. I think there in equilibrium.

4. Aug 9, 2010

### Staff: Mentor

Fair enough. I would think they are in equilibrium as well, since the system seems balanced. Even if the mass of the ropes is not negligible, the system still seems balanced.

5. Aug 9, 2010

### Staff: Mentor

Note, though, we don't know the weight of the boxes and regardless of their weight (unless they are negligible too), the ropes they are attached to can't be horizontal - they must sag.

6. Aug 10, 2010

### sfsy1

Why do they have to sag? I thought there's tension?

7. Aug 10, 2010

### cjl

In order for the sag to be zero, the tension would have to be infinite (or the boxes would have to be massless). This is because the vertical component of the tension is supporting the boxes, and if the rope is horizontal, the vertical component is zero.

8. Aug 12, 2010

### CountFleet

Thanks for all the replys! :) The way I have it though when you move one box the other one gets pulled in the opposite direction. Is there a way to get both boxes to move in the same direction?

9. Aug 12, 2010

### Staff: Mentor

Slack the ropes and push on the boxes directly or move the pulleys.

10. Aug 13, 2010

### CountFleet

Wouldn't slag put it out of equilibrium? How could you change the pulleys so both boxes can move in equilibrium in the same direction at the same time?