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B Impact force on falling egg?

  1. Sep 22, 2016 #1
    I searched engineering calculators and they rely on the input you know the stopping time or the stopping distance - easy for a car but not an egg.

    Knowing either of these quantities makes the problem trivial, but how to estimate or calculate them??

    What is the best assumption for either and how is the assumption justified for a free falling egg hitting concrete.

    I would like to do it theoretically and not use video or force sensors.

    Is this possible?
     
    Last edited: Sep 22, 2016
  2. jcsd
  3. Sep 22, 2016 #2

    phinds

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    If you can't solve a problem without a calculator you should not expect to be able to solve it WITH a calculator.
     
  4. Sep 22, 2016 #3
    Actually I just looked at how the calculator solved the problem ie what equations. I get the physics given impact time or distance - I have no idea how to get values for time or distance of stopping apart from measurement.

    If you can point me in right direction be appreciated.
     
  5. Sep 22, 2016 #4

    phinds

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    Is that single word response supposed to mean something?
     
  6. Sep 22, 2016 #5
    I have to post a random string then use the edit box to make the text not gibberish...tedious.
     
  7. Sep 22, 2016 #6

    phinds

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    That seems odd. How can you be able to post a string of gibberish but not instead post a real response?
     
  8. Sep 22, 2016 #7
    Don't know....but back to the question.
     
  9. Sep 23, 2016 #8

    davenn

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    you have to make some effort yourself.....
    list the things you know about the egg and its fall
    then you can figure out how to find the force that the egg hits the ground with
     
  10. Sep 23, 2016 #9
    Because a car a crushing distance is easy to estimate eg the crumple distance. Usually qouted around 0.5m.

    An egg??
     
  11. Sep 23, 2016 #10

    davenn

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    forget about the crumple distance at this stage ... lets initially treat it as a solid object

    again ...


    Dave
     
  12. Sep 23, 2016 #11
    Lands at speed root(2gh)
    Above some height h egg cracks on impact.
    No observable deformation, just catastrophic fracture.

    Nothing else I can think of.
     
  13. Sep 23, 2016 #12

    davenn

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    you haven't stated any of the things that need to be considered to work out the force of the impact

    here's some hints
    mass of the egg,
    height dropped from
    acceleration rate at the time of impact

    what is the formula for working out force of a falling object "in" gravity ?


    Dave
     
    Last edited: Sep 23, 2016
  14. Sep 23, 2016 #13
    All I got from that is;

    F=mass of egg x acceleration = mass of egg x velocity / time

    Initial acceleration = g

    velocity initial = root(2gh)

    velocity final = 0

    time from when egg hits ground until it stops moving ie collision duration I don't know and what needs to be known to work out impact force.
     
  15. Sep 23, 2016 #14

    davenn

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    try this .....

    Impact Force from a Falling Object
    The dynamic energy in a falling object at the impact moment when hitting the ground can be calculated as

    E = Fw h
    = m g h (4)


    where

    Fw = force due to gravity - weight (N, lbf)

    g = acceleration of gravity (9.81 m/s2, 32.17405 ft/s2)

    h = falling height (m)

    The equation can be combined with the equation of work to:

    F = m g h / s

    now using that work out the force
     
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