Boats That Float


Boats That Float

Do you ever wonder why a big heavy metal ship can float? If you threw a big piece of metal into the water surely it would sink. What if you threw a log into the water? Would the log sink or would it float? What does the shape of a boat have to do with floating?

Many people are confused about floating. This article will help describe why things float and will include experiments to be performed to further your understanding.

A balance between shape and weight needs to be met in order for an object to float. A large boat is obviously very heavy but is still able to float. If you dropped a ball shaped object of the same weight into the water, it would not float.

When a boat floats it pushes against the water around itself. In turn, the water around the boat pushes against the boat. The action of the water pushing against the boat is the force that holds the boat above the water. The key is the shape of the boat. The shape is relative to the weight of the boat. A very large, very heavy boat needs to have very high sides so lots of water can press against the sides and hold the boat afloat.

The second key to a floating boat is the air trapped inside the boat. The hull of a boat is hollow. This hollow space is full of air. Air is lighter than water. If the hull was solid metal the boat would not float.

Try this experiment:

Materials needed:

Two pieces of clay that are exactly the same weight (you could ask the post office to weight the pieces for you)
A large pot or bowl of water

Roll one piece of clay into a nice smooth ball.

Shape the other piece of clay into a boat shape with THIN walls. The bottom of the boat should be relatively flat.

Gently place both shapes into your container of water.

The ball will sink and the boat will float. Both pieces of clay weigh the exact same amount, but the boat shaped clay has more surface area in contact with the water. There is more water pushing the boat shaped clay up. The ball has much less area in contact with the water, so there is not much water holding the ball afloat.

A trip to the library might be fun to research the different shapes of boats. There are boats with pointed and flat bottoms. There are boats made of metal, wood, fiberglass, reeds and plastic.

The copyright of the article Boats That Float in Homeschool Science is owned by Lisa Hawkins. Permission to republish Boats That Float in print or online must be granted by the author in writing.

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