Energy Flow Investigation 6-2:

Experimenting With Equilibrium


A clear plastic container (such as a 2-liter soda bottle) has a series of holes about 1¦2 cm. in diameter. The holes are evenly spaced from top to bottom, about 2 cm. apart, in a spiral pattern around the bottle. Water flows continuously into the bottle from above, through a tube from a water faucet. Water flows continuously out of the bottle through the holes. A sink or large tub of water catches the water flowing out so it does not spill on the floor.


1. When the water is turned on, what will happen to the level of the water in the bottle?

2. What will happen to the water level if one of the holes is blocked?

3. What will happen if the water flows into the bottle faster? Slower?

Observe and Record

1. Turn on the water and adjust the flow so the water level stays constant. Mark the level with a piece of tape. What happens if you increase (or decrease) the rate of flow?

2. Block one or two of the holes. What happens?

Draw Conclusions

1. What is the relationship of the water level to the rate of flow?

2. What is the relationship of the water level to the number of blocked holes?

3. How is the rate of incoming water related to the rate of outgoing water?

4. Is this system in equilibrium? Why or why not? If it is in equilibrium, is it in static or dynamic equilibrium?