Technology

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Video

Materials

• Aluminum foil (or other material for the hull)
• 1 straw (or other material for the mast)
• 1 paper (or other material for the sail)
• Tape (or other material for attaching the mast to the hull)
• 1 pair of scissors
• 1 tub of water (or a pool, a pond or a lake)

Explanation

You have now built a boat, and one that (at least somewhat) is propelled by the wind.

It's very uncertain when humans first started using boats. Perhaps it was as early as 130,000 years ago, as some finds in Crete indicate. Or maybe it was around 40,000 years ago, when man first came to Australia. The oldest boat that has actually been found is dated to between 8040 and 7510 BC. It's 3 m (10 ft) long, was found in the Netherlands and consists of a pine trunk that has been made hollow. However, it's not entirely certain that the trunk was actually used as a boat. Maybe it was, for example, used as a food bowl for livestock.

A boat floats because its density is lower than water's. You can also explain it by the fact that the amount of water a boat displaces weighs less than the boat.

When it's windy, a lot of air collects behind the sail. This means that many air molecules are within a small volume and push on each other and what is around them. Therefore, the sail and thus the whole boat is pushed forward.

Test and improve

You have now built your first prototype. There are probably improvements to be made. In order to keep working on your design, try answering any of the following questions.

• How many coins can your boat carry before it sinks?
• How does the shape of the hull affect the boat's buoyancy?
• How high can you make the boat without it tipping over?
• What shape should the sail have, or how many sails should you have, for the boat to go the fastest?

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