Why does a boat float? Experiment with buoyancy.

Description:

Learn about buoyancy. Be able to answer the question: “How does a boat float?”

Equipment needed:

Play-Doh or some sort of modeling clay.

The Digital Bits Science Lab Experiment:

Roll your Play-Doh or modeling clay into a ball:

Drop it into water. You’ll see it sink:

Next, take another handful of Play-Doh – use the same amount as before. Make a deep boat-like or cup shape, something similar to what you see here:

And put it in the water:

Why does our boat float? This experiment demonstrates the concept of buoyancy. Also called the “Archimedes principle“, this is what happens when a boat is placed in water: The water pushes back! The Archimedes principle tells us that an object in liquid is pushed upward by a weight equal to the amount of water the object displaced.

To put it simply: When you put your boat in water, how much water does the boat “push” out of the way? Take that water, and weigh it. That weight is the same weight pushing the boat “up” out of the water.

So in this case, the weight of our displaced water (the amount pushed out of the way) was more than the weight of the Play-Doh boat. That’s why our boat floats!

Note that the experiment above was done with Play-Doh. And a word of warning – this experiment is messy! Play-Doh (and I would assume other modeling clays) is water-soluable, unless you mold and harden the clay before dunking it. So the longer you leave the Play-Doh in the water, the more it will turn into a gooey, sticky mess. Parents and teachers, you’ve been warned. Kids, you’ll love it!

Other articles related to this topic:

• Why is it easier to swim in the ocean? Learn about buoyancy.
• Power a boat with surface tension: Make a “zoomer”
• 1 cup and 1 cup does not make two cups – Experiment with solutions
• Duplicating the Greenhouse Effect
• Open your fingers and try to drop something: experiment with the body and its limitations