If I drop a box onto a moving conveyor belt - the sliding friction will do
POSITIVE work until the speeds match.
Yes, it’s relative to which reference frame is chosen.
On Apr 25, 2024, at 2:20 PM, stefan jeglinski<jeglin@4pi.com> wrote:
Would we say this is similar to friction? We say the work done by sliding friction is negative, and
we justify this by saying either that delta K is negative (object slows down) or the force is
pointed opposite to the displacement, but it still depends on our *belief* that the friction force
is pointed opposite to the displacement. In the annals of observation, this one appears to be
ironclad but it does sometimes seem lacking to just say "well if it weren't true then energy
wouldn't be conserved." If that's the best we can do then I'm good with it, but I do prefer to
level with a student that maybe "that's the best we can do."
Stefan Jeglinski
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