Hi All,
Comment on John Denker and William Beaty's discussion on direct and
indirect forces.
Surely this is not a matter of semantics. In theNewtonian model that
I and, I believe, many others use there are two types of force:
contact forces and
action-at-a-distance force. The former category include pushes and
pulls, the latter include gravitational, electrostatic and magnetic
forces.
I agree completely with William that there is no force, in the sense
of Newton's laws, between the hovering bird and the floor of the cage
just as there is no force between the two objects connected in an
Atwood's machine. So-called indirect forces do not fit the model and
certainly cause confusion in the class room, where they are a common
misconception.