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Kissing Apples

November 21, 2014 By Leave a Comment

What you need:Kissing apples
• Two apples
• String

What you do:
• Attach a piece of sting to each apple.
• Have each hand hold one string so that the apples  are at nose-level, 6″ apart.
• Blow hard between the apples and watch them move!

What should happen:
• The apples will get closer  to each other.

Why does that happen:
• The air pressure is lowered as you blow between the apples (think of the air molecules as ping pong balls … they balls don’t have enough time to touch the apple surface as they zoom by).
• The air surrounding the apples that’s not really moving is now at a higher pressure, and pushes the apples together.

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Air Pressure

November 21, 2014 By Leave a Comment

What you need:Air pressure1
• An empty bottle
• Foil

What you do:
• Roll up  a pea size ball out of foil.
• Place the bottle on the edge of a table.
• Put the ball of foil inside of the bottle neck.
• Try to blow the ball into the bottle.

What should happen:
• The foil ball shoots back out towards you.

Why does it happen:Air pressure2
•The same principles that keep airplanes in the sky also apply to this  experiment. The key point is that moving air is at a lower pressure than still air. This is the Bernoulli Principle. In the case of the  bottle the air that is blown towards the mouth is deflected around the the sides of the bottle (very little moves past the ball of foil). This means that the air pressure in front of the ball is lower than behind, and so the ball flies out.
Airplane wings are specially shaped so that air travels faster over the top of the wing than over the bottom surface. Again the pressure is lower above than below and the wing is “pushed” upward by the higher pressure air – called lift. The faster the plane moves forward the bigger the lift it experiences.

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