Re: Calculating Newtons in Joules and Joules/s


Dennis B wrote:
As a more realistic solution, I ask, would it be possible for physics
to function properly using only a measure of energy?

"Realistic" presumably means "matches reality". I'm not sure
exactly what you're claiming below, but I suspect from
the history that it won't match reality.

I ask becuse then
when we say that the two differing masses moving at different
velocities have the same value (of energy),

Do you really mean KE here, 0.5 mv^2? Or do you mean
the same value of mv?

they truly will exert the
same effects (thus, clearly having the same value).

Well, no they won't. That's the first place where your "realistic
solution" doesn't match reality.

For example, a 1kg
mass travelling at 2 m/s (having a kinetic energy of 2J)

KE = 0.5*mv^2 = 0.5*1*2^2 = 2 J. OK.

will exert the
same effects as a 2 kg mass travelling at 1 m/s (which also has a
kinetic energy of 2J).

Incorrect. KE = 0.5*2*1^2 = 1 J.

Nor will these two masses exert the same effects. They
have the same momenta and different KEs, and as
a result they will not have the same effect on other
masses in collisions.

This not only makes physics more intuitive, it
makes it simpler and easier to learn.

By substituting laws we know to be true and to match
reality, with other things which are provably false. What is
the point in teaching a "simpler physics" which doesn't
match reality?

Alas, what is the point of
specififying that momentum is the same if it does not exert the same
effects?

There are multiple effects. Figuring out exactly what
happens depends on knowing both the momentum and
the energy. I'm sorry, but that's just the way it is. Both numbers
affect what happens in collisions.

- Randy

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