Siphons

Water flowing uphill, for a while

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• A siphon’s outlet speed is $\sqrt{2gh}$, set by the drop below the tank surface.
• Atmospheric pressure pushes the water over the top.
• The hump can’t exceed about 10 m for water (the barometer limit).

Steps

1. Over the top
2. Draining a fish tank
3. How high can it climb?
4. What pushes it up?
5. Emptying the tank
6. A mercury siphon