Re: Setting up problems

[SSHS KPHOX <kphox@CHERRYCREEKSCHOOLS.ORG>]

Forum for Physics Educators <PHYS-L@lists.nau.edu> writes:
> The issue of not knowing the mass comes, I think, form not creating a
> culture of solving the problem by algebra first before putting in the
> numerical values.  This is always an uphill battle and depends on the
> symbolic math ability of your students.

It was so much easier to get folks to write out the equations and
manipulate them symbolically before the ever present and all powerful
calculator. We wanted to make it so we had fewer computations to do.

My face is still blue from asking students to write the governing equation
before substituting. Simplifying before substituting.

I am liking the idea of asking for students to write in this order:
a word/concept equation : the PE and KE at the start equals the KE and PE
together at all the other points.
a symbolic equation: mgh + 0 = 0.5mv^2 + mgH
simplify if possible: gh = 0.5 v^2 + gH
Now add numbers and solve though I'd prefer solve first.

On a perversely jocular note:
Now I am mean enough though that when a student says I left out the mass I
might say (even have said) "Egad you are right, let's see....its 1273.46
kg"...they are quite upset when they see the pain I put them through..heh
heh.  A lesson? I hope.

Ken Fox