Blow up two identical balloons to different sizes and pinch the ends. Connect their mouths with a piece of plastic or rubber tube (you may need two pairs of hands for this). Now let the air flow through the tube. What happens?
If intuition told you that the balloons would equalise in size, you'd be wrong. The small balloon forces its air into the bigger one. The pressure inside a balloonas in a bubbleincreases as its radius decreases. Try listening to what happens when you stretch the mouth of a balloon over a party squeaker. As the balloon deflates, the squeaker's pitch rises as air is forced out faster.
Tie one end of a piece of string to a stone and attach a ping pong ball to the other. Sink the stone slowly into a jar of water so that the ball floats beneath the surface. ...
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