Shape does not matter
Does liquid pressure change with the shape of the liquid column? Activity 15.1 tests it directly.
Activity 15.1
Obtain five tubes of different shapes, as shown by a, b, c, d and e in the figure.
Build a tube system by fixing them to a PVC tube that is closed at both ends and pierced with holes.
Now fill the system with water, stand it where it will not be disturbed, and measure and record the vertical height of the liquid column in each tube.
Figure to be added
| Place | Vertical height of the liquid column (cm) |
|---|---|
| a | measure |
| b | measure |
| c | measure |
| d | measure |
| e | measure |
The observation
The vertical height of the liquid column is the same in every tube.
What this tells us
We know that points at the same level in a liquid are at the same pressure, so the pressure must be the same at every place along the PVC tube where a tube is fixed. That the liquid stands at the same level in every tube therefore shows that the pressure depends not on the amount of liquid in a tube or the shape of its column, but on the liquid level alone.
Tube a in the figure holds more liquid than tube e, and the shapes of their columns are quite unalike. Yet the pressures at the foot of the two are equal.