Why Do Things Float? — Reading Comprehension

Some objects float on water, while others sink. The reason for this is called buoyancy. Buoyancy is the upward force that pushes objects up in a liquid, like water. When an object is placed in water, water pushes back against it. If the push from the water is stronger than the pull of gravity on the object, the object will float.

Another important word is density. Density is how much mass is packed into a certain amount of space. If something is less dense than water, it floats. If it is more dense, it sinks. For example, a wooden block floats because wood is less dense than water. A metal block sinks because metal is more dense than water.

Boats are a great real-world example of buoyancy. Even though boats can be very heavy, they are shaped to spread out their weight over a large area. This makes their overall density less than water, so they float. Ice cubes float in a glass because ice is less dense than liquid water. But a small stone sinks because it is denser than water.

When you get into a swimming pool, you may notice that you feel lighter. That’s because the water is pushing up on you with a buoyant force. This is why you can float or swim. Fish use buoyancy to move up and down in water by filling or emptying air bladders inside their bodies.

Understanding why things float or sink helps scientists and engineers design ships, submarines, and even life jackets. It also helps us stay safe in water and learn more about how nature works.

Interesting Fact: The largest ship ever built, the Seawise Giant, weighed over 650,000 tons, but it floated because its density was still less than water!

What is buoyancy?

What does density mean?

Which object will sink in water?

Why do boats float?

What happens if something is more dense than water?

How do fish change their position in water?

Ice cubes float in water. True or false?

What is the meaning of 'displacement'?