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Re: Car acceleration



I heartily agree that many such issues are clouded in semantic confusion. I
would enter that confusion by quoting the originally asked question: "What
force causes the car to accelerate forward?" By Newtonian definition (net)
force "causes " momentum change (F = dp/dt).
A closed system can "generate" internal kinetic energy of its parts by
internal transformation processes, but it cannot generate system momentum
changes (CM momentum) without somehow eliciting an external force upon
itself from some external agent. The car's frictional interaction with the
roadway serves this purpose and is in this sense the cause of the cars
momentum change (acceleration).

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
www.velocity.net/~trebor
----- Original Message -----
From: "Chris Horton" <ChrisAHorton2@HOTMAIL.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Saturday, February 02, 2002 7:55 AM
Subject: Re: Car acceleration


One could argue that E is the correct answer: The force of the foot on the
pedal causes a chain of events with the result that the car accelerates.

No, I am not just being facetious. The joker in this deck is the word
"causes". This word as commonly used (and I don't remember it being
redefined in any physics curriculum) does not preclude any number of
intermediate agencies, time delays, etc.

A better wording might be "What force acts on the car to accelerate it
forward?"
Chris