How It Works - - SCIENCE MYTHS -

There’s no need to fear for your life the next time you pass through the shadow of a skyscraper — pen­nies dropped from the rooftops aren’t go­ing to pierce your skull. In­trepid in­ves­ti­ga­tors have put this myth to the test in in­ge­nious ways, and it’s been well and truly busted.

Univer­sity of Vir­ginia physics pro­fes­sor Louis Bloom­field was so con­fi­dent that the myth was false that he sent a penny-loaded helium bal­loon into the sky. The pen­nies dropped like leaves in the air, buf­feted by the wind. The faster they fell, the more air re­sis­tance they ex­pe­ri­enced. Pen­nies are too small and flat to be a dan­ger, only reach­ing speeds of around 40.2 kilo­me­tres per hour. At some point the down­ward force of grav­ity bal­ances the up­ward force of air re­sis­tance, and the pen­nies can’t fall any faster.

Ac­cord­ing to the Mythbusters team, a penny dropped from the top of the Em­pire State Build­ing might col­lide with the pave­ment at 103.6 kilo­me­tres per hour. So they made a gun that could fire pen­nies at that speed. Al­though their test dummy may have suf­fered a lit­tle dam­age, when they turned on each other they were not harmed. Ac­cord­ing to Pro­fes­sor Bloom­field, if the coins fell in a vac­uum they’d be much more dan­ger­ous, reach­ing a speed of 335.7 kilo­me­tres per hour. But even then they wouldn’t pen­e­trate the skull.

How­ever, in an in­ter­view with Life’s Lit­tle Mys­ter­ies, he warned against ball­point pens. The shape of these is more bul­let-like, and if they come down straight they could get close to 335.7 kilo­me­tres per hour in the air, so the pointy end could do a lot more dam­age.

Coins tum­ble through the air, lim­it­ing their top speed

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