21 January 2006

Newton: Neither Cookie nor Cake

Dizzy asked: How is it possible that if I drop a bowling ball and a tomato out of my second-storey window at THE SAME TIME, they will hit the sidewalk at the SAME TIME TOO?

Thank you for the question, Dizzy. We can thank Isaac Newton (1643-1727) for the answer to this question -- which I do not pretend to fully understand.

Basically put, gravity acts on things in our world: objects don't really "fall," they are pulled downward. The larger the object (and more mass) the more gravity pulls it.

Air resistance also acts on falling objects. The larger the object the more resistance it encounters.

A bowling ball is heavier, so it is pulled faster. However, being larger, it meets more air resistance, which slows it down.

A tomato is smaller, so it is pulled slower. However, being lighter it meets less air resistance, which does not slow it down as much.

These two situations balance each other, allowing them to hit the ground simultaneously.

Newton never came up with a law to cover the amounts of damage caused by such an experiment, so I suggest it only be attempted by professional bowlers and farmers.


Confused Guy said...

What are "air rights"? How could you sell the "air" over your building? I've heard for years that New Yorkers are doing it, but how? Why?

Randy Santiago, Ft. Worth said...

At the close of his act, Jimmy Durante would always say "Goodnight Mrs. Callabash, wherever you are."
Who was Mrs. Callabash?

Roy said...

In fact, Galileo was the person credited with postulating that all objects fall at virtually the same rate with his Tower of Pisa experiment. Wind friction causes the "virtually" modifier, by slowing the rate of acceleration causing the object to land at slightly different times if their shape causes different wind resistance. A ball of wood and a ball of lead would have virtually the same wind resistance and would thus land so wind resistance would not be a factor. This was in the 1500's and predates Newton.

Newton gave us the Laws of Gravity and the rate at which objects fall, or are attracted to each other. F = G(Mm/r2)

He also extended the theory to celestial bodies. He calculated the path of the moon as a falling body and found that it should orbit the earth about every 28 days, which it in fact does. (a fairly comprehensive discussion is at http://www-spof.gsfc.nasa.gov/stargaze/Sgravity.htm .