A liquid presses too

Why do water tanks sit high on a roof? The tap on the ground floor gives a strong stream.

The rule

A high tank puts a tall column of water above the tap. So the pressure at the tap is high. A vessel is a container, such as a tank or a pipe.

A liquid presses on the bottom and on the sides. For the same liquid, the taller the column, the higher the pressure. The width of the vessel makes no difference.

Fill a narrow pipe and a wide pipe to the same mark. Each pipe has a balloon at its bottom. Each balloon swells, or grows bigger, the same amount. The wide pipe holds more water. Its balloon swells no more than the narrow pipe's balloon.

Holes in the side of a bottle spurt water sideways. So liquids press in all directions. A deeper hole spurts harder, because the pressure is higher there.

Pick a pipe. Add water. Watch the balloon and the jets.

Try the lab to finish this lesson.