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Q about momentum

  1. Mar 3, 2010 #1
    Hi,

    I'm discussing an issue on a forum with someone. I get the feeling that I am trying to be rational with this person while he is NOT being rational with me.

    This may sound a bit dumb, but it's kind of like a fantasy forum. In the story in question, the main character stops a sword blow which has been described as having the power of 1 million sword swings.

    I thought this sounded really stupid cause I know 1 million is a really big number. I'd like to use a bit of physics so show just how dumb the idea really sounds, but I myself am very stupid.

    I calculated that an average person with a weight of 70kg x 1 million would weigh 70,000,000kg. However, a sword swing also has momentum, so the weight of the strike would actually be greater than 70 million kg, right?

    This is on the assumption that the sword swinger is putting all of his 70kg of weight behind the swing, which may not be accurate in a real life context, but in the context of the story I think it is accurate. The context of this scenario is that all of that power is accumulated into a single blade which is swung at it's target.

    What I'd like to know is that if, at a distance of roughly 5ft between the two characters, the attacker starts his swing with the power of 1 million men weighing 70kg, how much power is he likely to have at the time that he actually hits the other person, according to the laws of momentum?

    Sorry, but I don't really know at what rate he accelerates or if that is even an issue in this equation.


    Anyway, thanks for any input offered.
     
  2. jcsd
  3. Mar 3, 2010 #2
    Best post of the day.

    EDIT: If he weighs 154,323,584 pounds he could just lay on the guy (if he doesn't fall through the earths crust). Also, a fat guy swinging a sword is the same as a skinny guy swinging a sword.
     
    Last edited: Mar 3, 2010
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