Moment of Science: The Penny and the Elevator

“Every time it rains, it rains pennies from heaven...” -Louis Prima
Could dropping a penny off the Empire State Building kill someone? Could jumping in a falling elevator save your life? ⬇️⬇️⬇️
Published: Sep. 20, 2022 at 10:26 AM EDT
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We’ve explored plenty of subjects revolving around gravity -- in some cases, literally -- but today, it’s a two-for-one special on morbid curiosity.

Part One: Could a penny falling from the Empire State Building kill a passerby on the ground?

The building was the tallest in the world for over 40 years, so it always seems to pop up in this hypothetical. There are two observation decks, but the higher one stands some 1250 feet above the streets of New York. Here’s the formula for calculating the speed as an object reaches a certain point (like the ground): V = Vo + gt. You find your starting velocity, Vo -- in our case, zero, since we’re just dropping it off a building, easy math there -- and take the time it takes for the object to fall (t), and multiply it by the acceleration due to gravity (g). In a complete vacuum, it would take that penny about 9 seconds to hit the ground -- but it could be a feather or a bowling ball, they’d all hit the ground at the same time and speed. The ballpark figure for that “g” is about 9.8 metres per second squared, and switching up some units gets you a final speed for that penny of just under 200 miles an hour. That would be downright dangerous walking under it... if it weren’t for a little thing called “air resistance”! That leads to an object reaching equilibrium, falling at a constant speed and no longer accelerating. The “terminal velocity” of a penny is somewhere between 50 to 65 mph -- barely reaching severe storm wind speeds, and certainly not penetrating your skull at that weight and size.

Let’s say you’re done flinging pennies off the building and being a general public nuisance, when suddenly... the elevator cable snaps and all the fail-safes fail to save you. Welcome to Part Two: Can jumping at the last second save you from dying in an elevator plunge? This same shaft has some precedent: In July 1945, an Army plane struck the Empire State Building while flying in fog, severing the main and safety cables and sending the cart into a 1000-foot freefall. The cables coiled up like springs on the bottom, and that -- combined with the air pressure of the shaft -- helped cushion the fall. Betty Lou Oliver holds the world record for longest survived elevator fall. Let’s say NONE of those are working, and a sudden stop awaits you. The highest human standing jump is 67 inches... and doing some math, they would’ve left the floor at... 13 mph. Good luck mitigating that freefall. Your best bet would be to lie flat, spread out the impact, and hope for the best.

It’s important to note that modern elevators have so many backups and fail-safes and brakes and springs, that at this point... you’re probably more likely to get hit by that penny.

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