91热爆

You will need:

• 听Cotton reel
• Elastic band (about 8-9cm long)
• Matchstick or toothpick
• A long candle
• Strong sticky tape

This activity will require an adult鈥檚 assistance to cut a short piece of candle wax.
A cotton reel tractor is a toy made by threading an elastic band through the middle of a cotton reel, and looping it through a matchstick, which is used to 鈥渨ind鈥� it up. But, in between the cotton reel and the matchstick, you need a nice smooth contact. So let鈥檚 start by making that.

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Take your candle, and snap it in half. Pull out the wick from the bottom half, so there is a hole down the middle. Now, ask an adult to carve a piece of candle for you about half a centimetre wide, so you have a button-sized circle of wax with a hole in the middle 鈥� like a washer.
Now, thread your elastic band through the cotton reel and the candle-washer, and on the other side of the piece of candle, attach the band to your matchstick. Tape down the end of the elastic band on the other side of the cotton reel. Your tractor is ready to wind up!
Wind the matchstick round and round so that the elastic band twists inside the cotton reel. You should feel it getting tighter and harder to turn. When you鈥檝e twisted it as much as you can, place the cotton reel on a smooth surface, and let go!

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What鈥檚 happening? As the rubber band twists, it鈥檚 storing potential energy. When you let go, that energy is released as kinetic energy. As the band untwists, the cotton reel moves.

You will need:

• Film canister with lid
• Fizzy vitamin C tablet
• Water

This activity needs to be done outside, and somewhere that any mess can be easily washed away!

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In a car, petrol is burned, producing a gas. As the gas expands, it pushes against pistons within the car engine, making them move. That movement is transferred through components of the car to move the wheels.听 In this activity, you鈥檒l see how producing a gas can make something move 鈥� quite spectacularly!

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Fill the film canister half-full of water, and put it on the ground. Now, take your fizzy vitamin C tablet, and very quickly, put it in the canister and put the lid on tightly.听 Now, step back and watch what happens!

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What鈥檚 happening? When the tablet is put in water, a chemical reaction happens which releases carbon dioxide gas. As more and more of the gas is released, the pressure inside the canister increases, until the lid is forced off with a pop!听

Have you ever been a passenger in a car that鈥檚 moving fast around a corner, and felt yourself sliding to one side? This activity shows the same forces at work.

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It鈥檚 best to do this one outside, in an open space.

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You will need a bucket of water, with a strong handle. Fill your bucket with water 鈥� about half full will be fine, you need to be able to lift it easily. Then, pick the bucket up by the handle, and swing it.听 Let your swings get bigger 鈥� and then, try swinging it around in a complete circle so it goes upside down above your head. If you鈥檙e spinning the bucket quickly enough, you should stay completely dry!

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What鈥檚 happening? When you swing the bucket in a circle, your hand is pulling inwards on the handle of the bucket. (That's what makes it travel in a circle, rather than fly off in a random direction). Due to the laws of physics, whenever you push or pull something one way, there's always an equal push or pull in the opposite direction. So, imagine the point when the bucket is completely upside down; at that point, your hand would be pulling the handle of the bucket vertically downwards. This means there's an opposite push, pushing the bucket and water in the opposite direction, upwards. This upwards push ends up being stronger than the pull of gravity, and so the water doesn't fall out of the bucket.