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Re: work done by friction



At 5:47 PM +1000 10/25/99, Brian McInnes wrote:
>More generally, friction between A and B does work on A if B is moving.

John, you have missed the point I was making. I'm claiming (as does
Arons in his "Guide to Introductory Physics Teaching.") that that no
work is done by the frictional force when A and B are in contact and
are moving relative to one another and, as usually happens, a
frictional force is present.



Hold on now. Does Arons REALLY say this?

Consider a 'conveyor belt' A, onto which box B is dropped (from an
infinitesimal height and with zero momentum in the direction of the
conveyor belt.

How does this 'no work done by friction' viewpoint treat the gain in
momentum and KE of the box?

FBD of the box only includes 'weight' and friction (initially kinetic).

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