The effect of drag

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I enjoyed your little article using falling pumpkins to illustrate gravity at Carnegie Science Center ("Pumpkin Drop at Carnegie Science Center Illustrates Explosive Joy of Gravity," Nov. 4). However, I wanted to point out that size does matter. In Galileo's Tower of Pisa experiment, the two balls he supposedly dropped were the same size, but their mass or weight was different. Indeed, if you drop a beach ball that weighs the same as a golf ball out the window, you will certainly see the golf ball hit first.

Shape and size affect the way that drag (or friction) works on an object. This is why parachutes work. Heavy objects that are the same shape as light objects fall at the same rate, but the theory does not apply if they are differently shaped or sized.


The writer is a professor in the math department at the University of Pittsburgh.



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