Good post Neil and here is some discussion from Rick B. He is also looking for some stuff he wrote on Kinetic energy.

“Before I respond to your excellent post, which I am by no means rebutting, I would like to point out a common error that a lot of people make when applying physics formulae.

The formula "F=ma" (Force = Mass * Acceleration) is NOT USED to calculate the force DELIVERED by the accelerated object, nor the

kinetic energy it accumulates by being accelerated. The formula F=ma is used to calculate the FORCE REQUIRED TO ACCELERATE the MASS.”

Rick Bottomley: Acceleration is = Dv/ Dt or change of velocity with respect to the time taken to affect that change. Note: Dv is not sign dependent, it can apply to an increase in velocity as well to a decrease in velocity. Therefore, it can also be used to calculate the force to de-accelerate a body in motion and in the case of a strike, the target body has to absorb that amount of force to bring the strike to a rest condition.

Also, I like to use the force equation because it helps to explain one of our principles; "to land on the weapon", which relies on the acceleration of gravity to generate additional force when we deliver a blow in this manner. I don't think I am applying it wrong in this application or bathroom scales wouldn't work.

“Take your train analogy for example. The train has a mass of "x". You want to accelerate it at a rate of "a-per z's" The formula tells you how much FORCE is REQUIRED to get it going there, not how much energy it will carry due to its movement.”

Rick Bottomley: It tells you exactly how much force is required to stop it or how much force the train will deliver to an object before coming to a rest

“This is one of the most often-quoted and most-misunderstood formula of all time.Incidentally it is known formally as Newton's Second Law of Motion, which you can look up in any high school text if you wish to verify this.”

Rick Bottomley: I believe that I am applying the force equation correctly

“A better formula for your purpose is K= (1/2) mv2 "KINETIC ENERGY= 1/2 of the MASS, times the SQUARE of the VELOCITY.

It is kinetic energy that a moving object delivers when it hits something. Velocity is easier to use in calculations because it is a constant speed, not a rate of change, as is acceleration. Note that the formula immediately discards one half of the mass.

Unit of ENERGY": joule. (1 joule is the energy needed to push with a force of one Newton over a distance of one meter.)

Unit of FORCE: Newton: The force it REQUIRES to accelerate one kilogram from rest to a VELOCITY of meter/secon, in one second's time.”

Rick Bottomley: Kinetic energy is an excellent formula to use a tool to improve the effectiveness of ones blows or strikes. I don't use this principle in a karate setting as most people don't have an intuitive feeling or understanding for "energy" (joules).

Good discussion folks.