Thought for the Week

By Ed Hall, Ni-Dan
Titusville Karate Dojo

Momentum

The dictionary defines momentum as: the motion of a body equal to the product of its mass and velocity. Let us say the arm has a mass of 10 pounds. By standing still and striking at a velocity of 40 feet per second, the total momentum will be 400 ft-lbs./sec (10 times 40). On the other hand, let us say the body has a mass of 170 pounds. By stepping in and striking at 40 feet per second, the total momentum will be 6800 ft-lbs./sec (170 times 40). In the second case, the whole body is used as the strike. The difficulty in achieving this ideal is that we must step first. We can't just pick up the whole body and throw it at the target, the body must arrive at the target still standing and in control. The phrase we hear constantly is "Step first, then punch". Upon first learning, the timing of this shift is a two-part move - 1) step 2)punch. Because of the pause, the momentum drops back down to, at maximum, 400 ft-lbs./sec. With years of practice, the timing of the transition of "step-then-punch" becomes fluid. Only then can we come close to maximum momentum. Carrying the case one step further, lets us say the attacker's body has a mass of 170 pounds, and he attacks at a velocity of 40 feet per second. By side-stepping in and counter-attacking at the same velocity the momentum becomes 46,240,000 ft-lbs./sec ! (170 times 40 times 170 times 40). Obviously, these are ideals, not correcting for gravity or friction and assuming the total transfer of momentum to the target, which is impossible.



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