Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Car acceleration



some one used a cog rail car, another a cable car, and another a skater and a
wall. Microscopically, I think these are the same and when not obviously the
skater, cog, etc. called static friction. What is the diff. between the
rough tire matching the rough road, or the cable clamp and the cable, and the
skater? If the skater's force fails it's because the wall broke (thin balsa
wood); clamp fails the steel is damaged -- heavily scratched; tire fail
--lay rubber.

bc


Bob Sciamanda wrote:

Gary Turner wrote:
. . .
Now, is that sufficient? Is the car going to move? I have relied on
>static friction only here and the end result is that the force is
between
the engine and tires.

Analyses of the internal forces between (or among) the internal parts of a
system (the car or the skater) will illuminate the mechanism whereby the
increased kinetic energy of certain system parts (tires; skater's arm) is
generated. This kinetic energy is internal to the system and will not
directly change the system (CM) momentum - as happens on ice, where much
KE is generated but no CM acceleration. These moving parts must then be
used (through mechanisms of friction, rigidity, etc) to elicit a force
from an external object in order to produce a momentum exchange between
the system and the external world.

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor