ChipB, Thank you for your comments and help.

My opinion is the quest of simpler math (avoidance of bottom rung calculus at least in the 90's, 10's) by HS physics has harmed science education. It has me upset. Nothing can be done, of course. I don't know you, You work hard at PHF. You can't do anything. Maybe I should just take a laxative (sp).

Originally Posted by **ChipB** I don't follow your equation 5, defining g_c. It's ... Why introduce it all? |

It was introduced in engineering texts until 98 I know. If you have not seen "g_c" you are lucky. I don't know if this is around anymore - I hope not.

Originally Posted by **ChipB** Also, your equation 7 is precisely the way that Newton wrote his law (though his calculus notation was a bit different). In most physics text books the law is introduced as F times t = change in momentum, or F = Delta momentum/delta t, which in the limit as t goes to zero becomes the derivative as you wrote it. If one assumes that mass is constant it makes the mathematics of solving high school physics problems much easier (similar to assuming acceleration is constant in using equations of motion), and so 99% of the time F=ma is correct for typical homework problems. Of course students should be reminded that the true 2nd law is as you wrote it. |

Thank you for this summary. I have only a few, older texts here. I think you have said: d(mV)/dt =sum(F) was Newton's form. One assumes he had a reason for placing "d(mV)/dt" left of equality. (My conjecture is momentum is a property and sum of forces is a construct). These days our physics publicists have adopted the form: "F = Delta momentum/delta t."

However, now as before, our equations read left-to-right. Newton's 2nd Law got "flopped" left-term-right" and "right-term-left" (so the equation tells what force is?). For the idea "sum(F)," a simpler term, "F" (called "net" ) was inserted. Force is a construct. A way to think; like double-entry bookkeeping.

"Easier math for HS students? Easier math to do easier physics? Easier than "what is a derivative?" Easier than Newton's definition of velocity. Easier than what Newton knew in 1680?

I fixed the "point of clarity," thank you. Ignore my typos, please!

Thank you, Jim Pohl