- #1
Leon4735
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Hi,
I am wondering how I can reconcile the concept of work as it is
introduced in mechanics with the way work is defined in thermodynamics,
as a transfer of energy. I would also like to maintain the convention
that negative work means a loss of energy, and positive work means a
gain of energy. The example I have been considering is an object
falling toward the surface of the Earth. In most textbooks, it seems
that the object+Earth as an isolated system in which mechanical energy
is conserved. Does the concept of work have any meaning in an isolated
system? When an object falls the gravitational force acts along a
displacement, so it seems like work is done by the gravitational force
on the object. If so, where is the energy being transferred from? If it
is transferred from the gravitational field, the field loses energy;
shouldn't the work done by gravity be negative? But the force and
displacement of the object are in the same direction, so a conventional
calculation gives a positive work.
If anyone has any thoughts as to how these ideas can be made
consistent, or where my thinking is flawed, I would greatly appreciate
it.
Thanks - Leon
I am wondering how I can reconcile the concept of work as it is
introduced in mechanics with the way work is defined in thermodynamics,
as a transfer of energy. I would also like to maintain the convention
that negative work means a loss of energy, and positive work means a
gain of energy. The example I have been considering is an object
falling toward the surface of the Earth. In most textbooks, it seems
that the object+Earth as an isolated system in which mechanical energy
is conserved. Does the concept of work have any meaning in an isolated
system? When an object falls the gravitational force acts along a
displacement, so it seems like work is done by the gravitational force
on the object. If so, where is the energy being transferred from? If it
is transferred from the gravitational field, the field loses energy;
shouldn't the work done by gravity be negative? But the force and
displacement of the object are in the same direction, so a conventional
calculation gives a positive work.
If anyone has any thoughts as to how these ideas can be made
consistent, or where my thinking is flawed, I would greatly appreciate
it.
Thanks - Leon