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A long time ago I had this discussion with some people if throwing a coin of a building is dangerous (potentially deadly) if it hits someone. The height of the building should be skyscraper-like so the coin could reach 'terminal velocity'.

From the material most coins are made up it is pretty obvious that it should be dangerous, but from its shape I assumed that it might not fall straight down but to start gliding somewhat like paper, but not as wobbly of course.

Is there any info available on this?

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  • I think it is dangerous (the terminal velocity is likely to be high), but I am not aware of any experimental data. For me the closest known situation is: skeptics.stackexchange.com/questions/610/…
    – Suma
    Jan 5, 2012 at 11:34
  • MythBusters say "NO"
    – Oliver_C
    Jan 5, 2012 at 11:36
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    Mythbusters say not deadly, but this is definitely dangerous, as it would be if you throw a coin at someone in the street.
    – Rory Alsop
    Jan 5, 2012 at 13:15
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    @Suma: I've seen that question, but bullets are very aerodynamic, rotate and built to penetrate skin and bones.
    – Baarn
    Jan 5, 2012 at 13:40
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    The notability of this question has been challenged. It is such a common myth, I never felt the need to establish the notability. JayPinkerton.com not only evaluates the claim, but claims it to be notable: "Ask any child on the playground and odds are they've heard the one about the penny dropped from the top of the Empire State Building — the penny that fell with such velocity it went right through someone, killing them instantly."
    – Oddthinking ♦
    Feb 1, 2012 at 13:36

1 Answer 1

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These guys measured a penny's terminal velocity: A Penny in Free Fall There are several ways a penny can fall, so they report terminal velocities in the range of 20-45 mph (9-20 m/s). That's fast enough to put an eye out. Copper pennies, pre 1982, fall faster than post 1982, zinc pennies.

[...] a penny falling at terminal velocity will not kill a person. After reviewing the table of terminal velocities, a penny may fall faster than a Ping-Pong ball, but certainly not any faster than a basketball. These terminal velocities convert to about 20-45 mph (32-72 km/h). This may cause a bit of a sting, but it is not going to kill a person.

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    The Mythbuster video came to the same conclusion, assuming even higher terminal velocities (up to 55mph). So I think this answer is what I can accept. Thanks.
    – Baarn
    Jan 5, 2012 at 14:04
  • I think this is even better than Mythbusters, as they seem not to have measure a terminal velocity, only replicate its effect. (I did not understand from watching the episode how they obtained the 55 mph value. Did they explain?)
    – Suma
    Jan 5, 2012 at 15:52
  • they used a vertical windtunnel IIRC
    – ratchet freak
    Jan 5, 2012 at 18:21
  • From watching the link provided below my question, I thought they just calculated the speed for coins falling 'flat' and 'straight'.
    – Baarn
    Jan 5, 2012 at 18:28
  • This is wonderful; my dad has always related a story of a friend of his who used to work on very high equipment for building construction and said if a penny was dropped, it would dent the concrete below.
    – Hendy
    Jan 7, 2012 at 14:34

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