Tristan’s Water Wheel

Tristan and Elsa help Grandad set a small wooden water wheel above a shallow tray. It turns freely on a short axle when Tristan pushes it gently with one finger. Elsa brings a jug of water, excited to see whether the moving water can make it turn without their hands.

Tristan pours the first jug straight through the empty space beside the wheel. Water splashes into the tray, but the paddles hardly move. Elsa suggests pouring faster. Grandad asks them to look at where the stream lands before using more water, because speed may not be the only problem.

They take turns pointing to the broad paddles around the rim. Most of the first stream missed them completely. Tristan remembers how a push from his finger made the wheel turn. The water must push against a paddle too, rather than simply passing through the gap beside it.

Elsa holds the jug above one side and tips a small stream onto the upper paddles. The wheel begins to move, and the stream catches the next paddle as it turns. Tristan kneels beside the tray to watch, keeping his hands away so he can tell that the water is doing the work.

The wheel slows when Elsa’s jug becomes nearly empty. Tristan fetches water from the bucket, but Grandad asks them not to pour two jugs at once. They can keep the test clearer by using one steady stream and changing only one thing at a time.

They try pouring onto the other side. Now the wheel turns in the opposite direction. Elsa draws a curved arrow on paper to remember each test, while Tristan points to where the stream met the paddles. The same wheel can move differently when the push comes from another side.

Grandad helps them pour the tray water back into the bucket for another turn. They work out a simple routine: fill the jug, choose a side, pour steadily and watch. Nothing has to be thrown away after one test, and the garden table stays much drier when they slow down.

Before packing up, Tristan draws the wheel with water landing on a paddle. Elsa adds the empty gap where their first stream fell. “More water was not our first answer,” she says. Tristan nods. Finding the right place for a small push changed the whole experiment.