What it shows
The shape of a boat decides how much it can carry. A wide boat with high sides pushes aside more water and so carries more than a flat sheet.
The science
A boat floats because the water pushes up on it. A wide, deep boat pushes aside a lot of water and gets a big upward push, so it can carry more weight. A flat foil sheet pushes aside little water and sinks quickly. The same foil can sink or float depending on shape.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- Three squares of aluminium foil of the same size, about 15 cm (free from kitchen)
- A big bowl or bucket of water
- Ten to twenty small coins
- A towel
- Paper and pencil to record
Safety
For this project: An adult must supervise near water and wipe up spills. Keep coins out of the mouths of very young children.
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.
All the safety rulesStep 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.
Lay out three equal squares of foil on the table.
Leave the first one flat. Fold the edges of the second one up a little to make a tray.
Fold the third one up tall at the edges to make a deep boat with wide base.
Float the flat foil on water and add coins one at a time. Write how many it holds.
Do the same for the tray boat and write the number.
Do the same for the deep boat and write the number.
Put the boats in order from the one that carried the most to the one that carried the least.
Try a boat with a pointed front and see whether it carries more or fewer coins.
What you should see
The flat foil sinks with one or two coins, the tray holds more and the deep wide boat holds the most. Your chart records each count.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1Why does a boat float?
The water pushes up on it.
2Which boat carried the most and why?
The wide, deep boat, because it pushes aside more water.
3Does the weight of the foil change between boats?
No, only the shape changes.
4What happens when you put too many coins?
The boat sinks because the load is more than the water can push up.
Take it further
Try a boat of plastic sheet or a leaf boat, and test which material carries more.
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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