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Lamp tips over and hits the top of the head

  1. Dec 6, 2015 #1
    Imagine a lamp tips over and hitst the top of the head. the lamp weighs about 300 gram and the distance when it started to tip over and hit the head was about 15 centimeters. in the moment of the impact the lamp has tipped over excactly for 90 degrees. The material is Metal that deforms only very little.

    what g force did the impact have?
  2. jcsd
  3. Dec 6, 2015 #2


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    It depends crucially on the deformation of the metal and the floor. Absolutely no deformation would lead to "infinite" acceleration, but absolutely no deformation is impossible.
    As rough approximation: (braking distance)/(distance it fell).
  4. Dec 6, 2015 #3


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    You need to know how fast it was going right before the impact, and how long it took to stop.
  5. Dec 6, 2015 #4
    As braking distance I would take 1 millimeter for the deformation of the scalp and 1 millimeter for the deformation of the lamp.

    as falling acceleration we could take 10 m/s (falling acceleration)

    the time it took to stop is hard to estimate
  6. Dec 6, 2015 #5


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    10m/s is a speed, the gravitational acceleration in free fall is 10m/s2.
    The lamp is not in free fall, however, as its base always has contact to the floor. It is possible to get a good estimate of its speed (if you know its mass distribution and so on), but I don't think you care about a factor of ~1.5 here, so assuming a free fall gives a reasonable estimate. There is a simple formula to find the speed of an object after falling down a given height. This will also help to find the stopping time.
    Alternatively, you can directly use the approximation I gave in post 2. It assumes uniform deceleration which is probably not true either, but precise values are much more work.
  7. Dec 6, 2015 #6


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    You can estimate the deceleration that the lamp will experience and express that in terms of g, but perhaps you care more about the head?
  8. Dec 6, 2015 #7


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    Somebody else's!.
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