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Why wont my Karate chopping hand pass through the table?

  1. Dec 26, 2011 #1
    In his PBS series videos, Brian Greene states the reason being electromagnetic forces between the charges in my body and the object (falling human and the ground in this case)

    In her book 'Warped Passages', Lisa Randall states the reason being the Pauli's exclusion principle for the fermions in our body.

    Are both the ways of looking at it correct? Or are they complimentary and have a connection?
  2. jcsd
  3. Dec 26, 2011 #2


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    This is based upon physics of course, as everything is, but the answer is more in the engineering realm. The structural integrity of the table is much higher that that of your hand.
    I'll let one of the educated folk take over from that.
  4. Dec 26, 2011 #3
    Yes, that does play a part. But at the atomic level, what causes this said effect?
  5. Dec 26, 2011 #4


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    You can pretty much look at it as electromagnetic interactions. The Pauli exclusion principle is really only talking about single atoms and when you're talking about macroscopic objects interacting, that's not something that needs to be taken into account.
  6. Dec 26, 2011 #5


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    To my understanding it is the electromagnetic force that keeps your hand from moving through a table, and it is the pauli exclusion principle that gives atoms a "size" bigger than a hydrogen atom, in addition to other things. Is the PEP the reason behind all of chemistry since it forces electrons to occupy different orbitals and hence determines their different chemical properties?
  7. Dec 28, 2011 #6
    If it's a real question of what it takes for a person to strike a wooden board (or table) in a Tae Kwon Do or Karate manner - and break through it - then the physics is fairly straightforward. The energy required to break a board can be determined from its material properties - specifically the impact strength. The deformation energy involved in such a collision can be derived from the conservation of energy and the conservation of momentum. What remains then, before attempting the break, is a check that the karate hand can physically achieve the speed and mass needed to exceed that deformation energy level. It's good to check these things because failure is more painful than success. (As Newton would tell you had he been interested in the martial arts.)
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