• Question: if you dropped a stone from the eitfell tower , and if it hit someone on the head , would it quite possibly kill them??? hmmm....

    Asked by claudzxoxo to Arlene, Colin, David, Eugene, Paul on 14 Nov 2012.
    • Photo: David McKeown

      David McKeown answered on 14 Nov 2012:

      Yes, I think it would definitely kill them. The stone would be falling very fast when it reached the ground. I calculated that if there was no air (and therefore no drag to slow the rock down) the rock would hit someone’s head at about 287kmph! (see below, for the calculation). Because there is air, the air slows it down a bit, how much depends on on the shape of the rock. It would still be going very fast even in air, so I think that it would be enough to kill someone.

      Calculation:
      The Eiffel Tower is 324 metres tall
      and the rock will accelerated towards the ground at 9.8 m/s^2 because of gravity

      The speed of the rock at the ground is calculated as the square root of (324*9.81*2) = 79m/s which is about 287 kilometres per hour

    • Photo: Paul Higgins

      Paul Higgins answered on 15 Nov 2012:

      Yes, it depends on the shape/size of the rock and the density of the rock. An irregular, not very dense rock (like micah, for instance) would probably slow down a lot from the air. Also, a big heavy rock (granite?), or a long sharp rock would be more likely to kill someone. I had always thought a coin being thrown off a building would kill someone, but recently I heard that isn’t necessarily the case… In any case I would not fancy getting hit in the head by a rock going any speed, if it doesn’t kill you, it could give you brain damage or a nasty concussion!

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