Re: [Phys-l] irresistible force v. immovable object

[carmelo@pacific.net.sg]

It can be physics. It is about "infinite momentum" versus "infinite inertia".
The result is "infinite energy transfer".

This may illustrate the problem of idealization.
However, there are other higher priority questions for the students.


Alphonsus

Quoting Mike Viotti <mike.viotti@gmail.com>:

> I totally agree that situations like these present teachable moments, but
> they're not physics.  By definition they can't be!  We can't have an
> unstoppable force.  We can't have an immovable object.  Use the student's
> question to foster critical thinking, fine.  But it's not physics.  By
> pretending that it is, we're really depriving the student the clarity he/she
> deserves.  We say that physics is used to model the real world, so how can
> we possibly extend its uses to something that is not an element of the real
> world?
>
> Massless pulleys (etc.) are different, because we acknowledge that the real
> world doesn't exactly work that way, but we have to start with simple cases
> and work our way up.  We are honest with students about this; we don't pull
> the wool over their eyes.  In my view, there is a distinct difference
> between approximations that simplify a complex problem to a manageable one
> and artificial constructs that attempt to physically explain something that
> cannot possibly exist.  The separation between those two groups is not
> trivial.