Sink or Float Tray
✨ A big plastic lid rests on the water while a tiny coin drops straight to the bottom.
🧰 You need
- a large bowl of water
- a spoon
- a plastic bottle cap
- a coin
- a small stone
- a leaf or a piece of paper
⚠️ Stay with an adult near any bowl of water and wipe up spills so nobody slips.
👀 What you will see
Wide, hollow and light things stay on the surface, while small heavy things like the coin and the stone go straight down. When you push a floater under and let go, it pops back up. Size alone does not decide the answer.
🧪 Do it
- Fill the bowl with water and spread an old towel underneath it.
- Hold up one object and say out loud whether you think it will sink or float.
- Drop it gently into the water and watch what happens.
- Put all the floaters on one side of the table and all the sinkers on the other.
- Count how many floated and how many sank.
- Push one floater right under the water, let go, and see what it does.
💡 Why it happens
Water pushes upwards on everything placed in it, and that upward push is called upthrust. An object floats when the water it pushes out of the way weighs as much as the object itself. A bottle cap holds a lot of air, so it is light for its size and the water can hold it up. A coin is packed tightly with metal, so it is heavy for its size and the upthrust is not enough.
🔁 Now try this
Screw one piece of foil into a tight ball and press another equal piece into a boat shape, then test both to see how shape changes the answer.
🤔 Think about it
A huge steel ship floats but a small steel nail sinks, so what is different about the ship?
🧘 Ask the Acharya
“A huge steel ship floats but a small steel nail sinks, so what is different about the ship?” — ask him and he will explain it from your own chapters.
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