Check It Out: What's Happening?

— You may have experienced the power supply of car models in your daily life. If you inflate a balloon and leave hold of, the balloon will fly around the room. What Because of the air pressure inside the inflatable balloon is more than the outside air pressure, and Happened this phenomenon is caused by trying to balance the pressure difference between inside and There? outside. As long as you close the opening of the balloon, the internal air will press against the elastic outer wall. Once you leave hold of the balloon, the air will flow out of the balloon at a very high speed. The same thing happens to your car. Why Do But or why can your CAr BE DriVen?Balloons Fly WhaT's the Use of Water? — If you try to drive a car with compressed air only and don't use water, you will find car can't move. Because of the force and reaction force in the experiment depend on the mass of the material sprayed by the nozzle. And since the quality of water is much higher than air's quality, the force that drives the car forward is also greater.

Tip

You can find more information about "Reflection in Nature and Technology" on page 15.

Reaction Force

Balloon rise

Force

air Outflow

BALANCE

= Balance of power

— The discharged air will produce a reaction force of the same magnitude, and the reaction force is opposite to the direction in which the air is discharged. Therefore, when air is discharged from the back of the balloon, the balloon will accelerate in the opposite direction.

You will need

Your PLASTIC BOTTLE with LITTLE AIR WATER SET, marshmallows, a piece of soft toast, and a solid object like a cube

Here's how

1. Cut a small piece of marshmallow and put it in the PLASTIC BOTTLE (Get help from adults). Assemble the PLASTIC BOTTLE and LITTLE AIR WATER SET together and put the RELEASE CLIP on the nozzle.

Now pumping about 80 times. Check the marshmallows. Has it changed? Then remove the RELEASE CLIP and see what happens.

2. Repeat the experiment. This time, put the cube, marble or similar solid into the

PLASTIC BOTTLE.

3. Now repeat the experiment again, this time, put a piece of soft toast into the

PLASTIC BOTTLE.

4. Then wash the PLASTIC BOTTLE.

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2

WHAt'S haPpEnInG?

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The more air pumped into the PLASTIC BOTTLE, the smaller the marshmallow. When you open the RELEASE CLIP, it will expand again until it returns originally. This is very similar to the air you pump into the LITTLE AIR WATER SET. The more water is pumped, the higher the degree of compression. On the other hand, cubes or marbles presents like water. No matter how often you pump, they will not change shape and size. Although the toast is soft, it does not change its shape. Because it is breathable, the pressure inside and outside the toast increases evenly.