image credit: Ed Lee
Demonstration of Aneurysms
How is an artery like a balloon? The photo (larger version) shows two partially inflated modeling balloons--the balloon begins to inflate at a weak point along its wall, and the wall bulges out, decreasing the pressure inside. For a discussion of this effect, including a video showing how the pressure in a balloon changes as it inflates, visit Demonstration of Aneurysms from Cambridge University. The same bulge happens in arteries. To learn about the physics of elasticity in balloon walls, see Wall Tension from Hyperphysics.
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Partly inflate a cylindrical balloon so that a nipple remains on the uninflated end. Press each part of the balloon. Is the air pressure the same everywhere inside? Pascal's Principle says yes--otherwise air would flow from high pressure to low pressure. When you press, could the stretched skin of the inflated balloon be putting a force on your finger? See Wall Tension from Hyperphysics.