Re: are normal reaction and tension conservative ?

[Ludwik Kowalski <kowalskiL@MAIL.MONTCLAIR.EDU>]

Ok, now you know that subject lines are not always displayed
entirely in lists of messages. And some people go directly to
contents of messages (ignoring the junk above).

> Are normal reaction and tension conservative ?

We say that a gravitational force is conservative because
the work done by it is zero along a closed path. A normal
force (a rigid floor acting on a rigid block) does not do any
work because it becomes zero as soon as your man starts
pushing it upward. I would say that the term "conservative"
is not applicable in this case.
Ludwik Kowalski

Chetan wrote:

> Consider the case of a plank (with a block on it ) at rest on the floor.
> the work done by normal reaction is zero.
>
> Now imagine  a man pushes the plank upward with an acceleration.
> Now the work done by normal reaction is nonzero.
>
> can normal reaction in the second case be considered non conservative.
>
> A similar situation is the case of a body at the lower end of a rope being
> pulled vertically upward by a man moving the upper end. could we label
> tension as non conservative?
>
> > Chetan wrote:
> >
> > > I think it depends on what forces are causing the normal reaction and
> > > tension(like when two masses are hanging on the opposite sides of a
> pulley
> > > then the tension in th rope is due to gravity which is a conservative
> force
> > > and so the tension is conservative).
> > >
> > > Is this right?
> ____________________________________________________________________________