Need help with a physics calulation

Discussion in 'Pseudoscience Archive' started by MacGyver1968, Jun 2, 2011.

  1. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

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    Assuming you have an object that weighs 80,000 kg, traveling at 223 meters per second...the kinetic energy of this object would be somewhere around 2 billion joules. right?

    If the striking surface area of the object was 500 square feet....what would be the psi or SI equivalent?

    Edit: the reason this is in pseudoscience is because it's a 9/11 question. I'm trying to determine the total PSI that the wings and fuselage of a 767 would impart on the perimeter columns.
     
    Last edited: Jun 2, 2011
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  3. James R Just this guy, you know? Staff Member

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    The energy doesn't help much here.

    The object has a momentum of p = mv = 80,000 times 223 kg m/s.

    The average force on the surface is:

    F = p/t

    where t is the time taken for the collision (roughly how long it took the 767 to come to rest from a speed of 223 metres per second).

    The pressure across the whole surface is:

    pressure = F/A

    where A is the total cross-sectional collision area (i.e. total cross-sectional area of the columns that impacted the plane, or roughly the cross-sectional area of the fuselage + wings as seen from the front).

    A bit more calculation can give you a ball-park estimate of the various numbers.
     
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  5. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

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    Thanks James.
     
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  7. adoucette Caca Occurs Valued Senior Member

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    Can't do it that way.
    Both the plane and the towers are too complex of a set of structures.

    See NIST NCSTAR1 Report 2 which goes into detail on the modeling of both the towers and the aircraft to determine the damage done by each plane to the respective towers.

    http://wtc.nist.gov/NCSTAR1/NCSTAR1-2index.htm
     
  8. AlexG Like nailing Jello to a tree Valued Senior Member

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    Can't do it that way. The wings and fuselage aren't solid bodies. They crumple and shred, and so don't transfer all their energy.
     
  9. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

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    I was just trying to get a ballpark figure....it really doesn't matter. I just found out the guy I was discussing this with is a "no planer", which renders him immune to math and physics.

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