Sink or Float For Kids

Why a ball floats in water & why a stone sink?


Take a jug full of water, put a tennis ball into it? What happens? Does it go to the bottom of the jug or it remain on the surface?

Now take a stone, put it in the same jug? What happens? Does it settle at the bottom or it goes down to the bottom?


You would observe that the tennis ball remains on the surface of the water, it is known as floating whereas the stone settles down at the bottom. Settling down at the bottom is called sinking. You can try the same experiment with other things also, some would float and some of them would sink to the bottom!

But have you ever wondered why it happens? Why the ball and the stone behave differently in water?

In the above video, you can learn about the reasons for the same. Two small kids would discuss and teach about this concept through many different experiments.

Why it happens?

Have you heard about density? Well, you need to know about density if you want to learn about the reasons for sinking and floating.

We all know that everything is made of small atoms (molecules). In few things, these molecules are jam-packed, that means that these molecules are very near to each other. Whereas in many things, these molecules are at a distance from each other.

This is known as density. The things where molecules are tightly packed are highly dense whereas where molecules are loosely packed, they have low density.

Here is a quiz for you:

Imagine you have 50 students in a room A and you have 20 students in room B. If the size of the room A and room B is same, which room is denser?

Answer is Room A because it has more students in the same area.

Hope now you’ve understood the concept of density!

Now you need to know two more things: gravity and buoyancy. Gravity is the earth force that pulls everything down whereas to understand buoyancy, you need to think about a situation.

Imagine trying to push a tennis ball into a jug of water. What happens? You will feel resistance from the water, won’t you? This upward force comes from the water toward the ball. This force is known as buoyancy.

If you have understood about the concepts of density, gravity and buoyancy, now it is time to watch the above video. You would learn that how interplay of these things decide which things would float and which of the things would sink in the water.

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