What it shows
A hand pump uses a piston and one-way valves to lift water from a well. The model shows how pushing and pulling the handle makes water move in one direction.
The science
Pulling the piston up reduces the air pressure inside the cylinder, so outside pressure pushes water up the pipe through the lower valve. Pushing the piston down closes the lower valve and forces water through the upper valve. Each stroke moves water a little higher until it flows out.
Materials
Cost: under Rs 200. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A cut plastic bottle as the cylinder (or a 50 ml syringe if a piston will not seal in the bottle)
- A rubber-sealed plunger from a syringe or cut rubber
- Two balloon flaps as one-way valves
- Flexible tubing
- A stick as the handle and a pivot
- A bucket of water and a jug
- Strong tape and glue
Safety
For this project: An adult must cut plastic and handle sharp edges. Work over a tray and keep fingers clear of the moving handle.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
Step by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Fix a one-way flap valve at the bottom of the cylinder where the inlet tube enters.
Fix a second flap on the piston or the outlet so water can leave but not return.
Attach the piston to the handle with a stick and pivot it on a stand.
Put the inlet tube into a bucket of water and pour a little water into the cylinder to prime it so the piston seals.
Work the handle up and down slowly at first.
Watch the water rise and flow out of the outlet.
Count the strokes needed to fill a cup.
Draw a labelled diagram and mark which valve opens on each stroke.
What you should see
Water flows from the bucket out through the outlet with each stroke, and the count of strokes per cup gives a measure of the pump’s performance.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
01What does a one-way valve do?
It lets fluid pass in one direction only.
02Why does water rise on the upstroke?
Lower pressure inside lets air pressure push water up.
03What limits how high a suction pump can lift?
Atmospheric pressure, about 10 metres of water.
04Why are hand pumps useful?
They work in villages without electricity.
Take it further
Compare a pump with a larger and a smaller cylinder and see the water per stroke.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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