Pressure II Segment 6: Pressure as a Force

Everyday Science

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.