As you walk down the city streets of Vancouver, is the fear of a penny falling from a skyscraper and hitting your head constantly on your mind? If so, walk freely friends. Studies have shown that a penny falling from any height will not be fatal. It is however strongly advised not to look up as a penny hitting your eye may not end very well…
The answer lies in the combination of the weight and shape of a penny. With a mass of 2.5 grams and a flat cylindrical-like shape, a penny‘s fall to the ground is merely a feather’s flutter; only faster due to its material density. It is this speed of a penny’s fall which fools the average person, letting them believe that it is indeed lethal.
As a penny falls, the coins flat surface allows for a greater surface area for increased air resistance. This resistance only increases as the coin increases its velocity, and said velocity increases until terminal velocity is met. Also, due to the coins little mass and high surface area, the air resistance works strongly upward against the downward force of gravity, minimizing downward velocity. “Thus, if hurled off a skyscraper, pennies achieve their terminal velocity after only about 50 feet (15 meters) of descent. After that point, they flutter to the ground at a measly 25 mph (40 kph)”, said Louis Bloomfield, a physicist at the University of Virginia.
The following is a video of the penny drop phenomenon, kindly demonstrated by the Mythbusters:
Keep in mind that this is focusing on pennies. Other small objects have been proven to be lethal (such as baseballs, pencils, nail-clippers, etc) and should not be tested unless in a controlled environment.
This idea of air-resistance slowing the fall of objects was brought to attention in the 17th century by scientist Galileo; saying that objects fall at the same rate due to gravity. We can prove this phenomenon by dropping objects in space with no air, or in other words, a vacuum.
This video compares two objects falling; first at regular atmospheric pressure with air resistance, then within a vacuum. Can you see the difference?
References
1. Scientific American. http://www.scientificamerican.com/article.cfm?id=could-a-penny-dropped-off (Accessed March 19th 2012)
2. Terminal Velocity. http://www.hyperphysics.phy-astr.gsu.edu/hbase/airfri2.html (Accessed March 19th 2012)
3. School of Champions. http://www.school-for-champions.com/science/gravity.htm (Accessed March 19th 2012)
4. How stuff works. http://science.howstuffworks.com/falling-bodies-info.htm (Accessed March 19th 2012)
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