What makes a balloon float? Well, there are three important forces acting on that balloon: gravity, pressure, and buoyancy. At Rice Elementary School in Wellington, Colorado, Brian demonstrates how these forces work on a balloon.
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In the Channel 10 studio, GPS units are used for another cool pressure experiment. GPS units can display the current elevation. How? It’s pressure!
Since air pressure is different at different elevations (high elevation = low pressure, and vice versa), the GPS units measure air pressure to estimate elevation. Want proof? When the units are placed in airtight containers, and the pressure is changed, the elevation changes. The units are “tricked” into calculating elevations several hundred meters lower and several thousand meters higher!
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Segment 7 Download Links
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LEAF BLOWER ELEVATOR
How can the air inside a tire support a tractor, or a school bus, or a semi trailer?! It’s because of pressure differences between the inside of the tire and the outside. Want proof?
Grace stands on a board which is on top of an airbag. When the bag is empty, the pressure isn’t strong enough to do anything interesting. But when Brian fills the bag using air from the leaf blower, the pressure inside the bag increases dramatically!
BUCKET BALLOON
When the bucket is low, the balloon doesn’t fill up — but when it’s high, the balloon does. Why? There are three important pressure zones here: the low pressure inside the bucket, the high pressure inside the balloon, and the low pressure outside the balloon. (The low pressure outside the balloon is in fact the same as that of the bucket, because it’s the same air.)
So, when the bucket is raised, gravity pulls the water down, making the pressure inside the balloon higher than the pressure outside of it. This allows the balloon to expand and fill.
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Now that we have discussed what pressure is, let’s find out what pressure does. First, Brian has a pair of translucent plates. He can remove all of the air from in between the plates. Now there is a very strong pressure difference! What will happen when Grace and Ellis try to pull them apart?
Next, marshmallows. They’re made with puffed air. What can we do to the air pressure to increase the size of the marshmallow?
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Segment 5 Download Links
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Little Shop of Physics 
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