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: Work/Energy theorem



Bravo, Dario! I have never liked the invocation of "pseudo-work", either.
Another argument goes thusly: All agree that the W-E th. can be applied to
a point particle. Well, each particle making up the object (car or person)
must have work done on it by a force if it is to accelerate. For most of
the particles this force is due to its neighbor particles . . . this chain
of forces must lead to that of an external agent - the internal forces
cancel to zero in their net effect. Each of these many forces does REAL WORK!

Bob Sciamanda sciamanda@edinboro.edu
Dept of Physics
Edinboro Univ of PA http://www.edinboro.edu/~sciamanda/home.html

Howdy,

Well, it's not quite that simple but almost. The work done by an internal
force is zero if the object is rigid; i.e., the relative position of the
particles in the object remain constant. If the object is non-rigid you
must take into account the work done by the internal forces. E.g., if the
"object" is two masses with a spring between them (or two molecules held
together with a Hook's Law type force) that internal force may do work.

Good Luck,

Herb Schulz
(herbs@interaccess.com)