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Re: Car acceleration



How does looking at the question from an energy standpoint change things?
The only choices given involve forces as long as a level road can be assumed
I see no other cause for the forward acceleration?

Cliff Parker

Never express yourself more clearly than you can think. Niels Bohr
----- Original Message -----
From: "Gary Turner" <turner@MORNINGSIDE.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Friday, February 01, 2002 5:11 PM
Subject: Car acceleration


I came across this question in an FCI-type set of questions:

A car accelerates forward from a stop sign. Air resistance slows the
motion. What force causes the car to accelerate forward?
A) It's weight
B) The force of the engine on the tires
C) The friction on the car from the road
D) The upward force exerted on the car by the road
E) The force of the driver on the accelerator pedal

When I first read this, I thought I got the answer (which was the
'correct'
answer). That is below. Then I thought about it some more from an energy
standpoint - now I'm not so sure. What does the group think?








Answer: C