|MadSci Network: Physics|
This idea is similar to the experiment Galileo designed which showed that if you drop 2 objects off the Leaning Tower of Pisa, even if they have different weights they will hit the ground at the same time (barring air resistance) because the acceleration due to gravity is a constant. Dropping different sizes of steel balls into a clear container of water (at different times) would be interesting because it would show that although they hit the water after the same length of time , they splash out different amounts of water because they have different momenta (plural of momentum) (mass times velocity) when they hit the water. If dropped from the same height, their velocity will be the same when they hit the water, but the momentum is different because the mass (or weight) is different. A similar and less messy experiment is to roll the balls down two different tracks (you can make tracks out of angle iron if you can cut the angle iron to a desired length) and have each ball strike an identical piece (both have same size and same weight) of wood (or soap, or anything that will slide with a small amount of friction. Dry ice (frozen Carbon Dioxide) would have a small amount of friction, but it would be hard to keep identical blocks of dry ice since the mass and size are changing continuously). The wood struck by the large ball should move farther, which again shows that even though the balls have the same velocity, they have different momenta, and the larger momentum will make the block of wood move farther on a horizontal surface.
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