Naked Science Forum
General Science => General Science => Topic started by: Jason Mallory on 25/01/2010 16:30:02
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Jason Mallory asked the Naked Scientists:
Hey Chris,
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Got a question for you, not sure you can answer it. I do Brazilian Jiu Jitsu and Wrestling and my question is :
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Who generates more force. The person in the top position with gravity and leverage or the person on the bottom with leverage and the power of the earth beneath him?
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I hope that makes sense. Most people think that the top person generates more downward force than the bottom person generates upward force. I believe it's the other way around but I don't have the physics to prove it.
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Hope you can help,
Jason Mallory
What do you think?
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I'd say that, assuming both players are evenly matched in terms of weight and strength, the uppermost person would have the uppermost hand, so to speak, owing to the effects of gravity. This is because once the person beneath is in a hold down, if we assume that the person on top has got them into some kind of lock, this is going to constrain their movements and ability to lever themselves against the floor, removing that advantage.
I have to admit that I only did about 2 years of Judo, so that's the limit of my expertise!
Chris
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Can somebody remind me of Newton's third law please?
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Let's say you lock up your opponent and takes him with you down on the mat, him being above. You will win if your lock is effective. Let's assume that you lose your balance and fall, your opponent following you down locking you up :). He will win if his lock is effective. There is no clear solutions to that one. As you say you can use the floor to leverage yourself and your opponent if he's above, but you will spend a lot of energy doing so. He won't spend as much working against you as his bodyweight (gravity) will hold you down. Consider a sumo wrestler falling above you :)
What would you expect your chances to be then?