What it does
Poke three holes down a plastic bottle, fill it with water, and the lowest jet squirts hardest. Pressure in a liquid grows with depth: the more liquid above a hole, the harder it pushes water out.
This page shows a 30 cm bottle with holes 5, 15 and 25 cm from the bottom. Drag the water level, let it drain, stand it on a box, or change the liquid. For each hole it shows the depth, the pressure there and where the jet lands. At Class 11 it adds each jet’s speed from Torricelli’s law, v = √(2gh).
It follows Class 8 Science, pressure, winds, storms and cyclones (liquids press on their container, more so deeper down), and Class 11 Physics, fluids (P = ρgh, speed of efflux). Before this, pressure explorer shows what pressure is; next, barometer altitude does the same for the air above us.
How to use it
- Choose a Level. Class 11 adds speeds and full working.
- Drag the water surface or use the Water level slider. Holes above the water give no jet.
- Untick Keep it topped up to let it drain. Fill to the top refills.
- Raise the bottle on a stand so jets fall further before landing.
- Pick a liquid: water, sea water, cooking oil or mercury.
Worked example
Full bottle on the floor. The bottom hole is 25 cm deep, so P = 1,000 × 9.8 × 0.25 = 2,450 Pa; the top hole has only 490 Pa.
At Class 11 the bottom jet leaves at v = √(2 × 9.8 × 0.25) = 2.21 m/s, the fastest. Yet it lands 22.4 cm away, while the middle jet lands 30 cm away, because the bottom jet is only 5 cm above the floor and falls in 0.10 s. On a 60 cm stand the jets land 80.6, 67.1 and 41.2 cm away, and the bottom jet wins.
FAQ
Does the jet speed change with the liquid? No. ρgh = ½ρv² gives v = √(2gh) for any liquid. The pressure does change: mercury’s is 13.6 times water’s.
Does the container’s shape matter? No. Pressure depends on depth, and acts sideways as well as down.
Is anything stored? No. Everything runs in your browser.
Where the numbers come from
- Pressure in a liquid P = ρgh, Torricelli's law v = √(2gh) from Bernoulli's equation, horizontal projectile motion (fall time √(2y/g), range 2√(hy)): standard school physics found in any textbook. g = 9.8 m/s² (rounded).
- Densities are rounded general values (water 1,000, sea water 1,030, cooking oil 920, mercury 13,600 kg/m³). The bottle, hole heights and drain rate are made-up teaching values.
- Checked by tests against hand-worked examples, the energy balance ρgh = ½ρv², and a step-by-step simulation of each jet's fall that does not use the range formula.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-10.