[Phys-l] scope of the course

[John Denker <jsd@av8n.com>]

On 02/05/2012 01:08 AM, Bernard Cleyet wrote:
> p.s. Since this is an intro prob.  i.e. algebra only, no calculus,
> one must assume the friction is constant.

I disagree, for at least three reasons.

*) The law for radioactive decay says the rate-of-change of x is
 proportional to x.  This is generally considered well within the 
 scope of the algebra-based physics course.  Viscous damping follows
 the same law.  Eddy-current damping follows the same law.

*) The case where the resistance is dependent on /position/ not
 velocity -- including the scenario where the block hits a peg --
 is well within the scope of the algebra-based physics course.

*) The original question came from a /college/ course.  At the
 college level, not all first-year courses eschew calculus.

======================

More importantly:  When solving real-world problems, it is
essentially always necessary to make assumptions.  Unless
you are quite sure everybody knows what assumptions are
being made, it pays to
 1) At least document what assumptions you are making.
 2) Preferably, check to see whether the conclusions are
  unduly sensitive to the assumptions.

To say the same thing another way:  If you've been warned that
people have been having trouble with a seemingly "simple"
problem, you could
 A) Assume they are all stupid, or
 B) Consider the possibility that the problem is ill-posed,
  and that different people are making different assumptions.
  Different is not necessarily wrong.