Originally Posted By: paul

Quote:
F=ma = 80m/s/s * 100kg = 8000N


change in velocity is not a force

Correct. And 80m/s/s is not a change in velocity, it's an acceleration. The change in velocity is only 80m/s.


Quote:

so force = d/(dt)*mv
F=40m/(40m*1s)*mv
F=40m/40 * mv
F=1*mv
F=1*100kg*40m/s
F=1*4000
F=4000N


In this statement of Newton's 2nd law, d is not distance, is part of the derivative symbol.

F=d/dt (mv)
m is constant so
F=m d/dt v
F=m dv/dt
dv/dt is, by definition, equal to acceleration
F=ma
Then continue as I've already shown recently.



Here's a quote from the very same page you referenced. Didn't bother to read any of the text with that equation?

"
the use of the constant factor rule in differentiation allows the mass to move outside the derivative operator, and the equation becomes
F=m dv/dt
By substituting the definition of acceleration, the algebraic version of Newton's second law is derived:
F=ma
"

Last edited by kallog; 07/09/10 08:01 AM.