[Physltest] [Phys-L] Re: projectiles

[Anthony Lapinski <anthony_lapinski@PDS.ORG>]

I teach high school physics -- no calculus. I was intending to give this
as a bonus question on a test, but I think it might be too difficult for
the majority of my students (even the honors ones).


Forum for Physics Educators <PHYS-L@list1.ucc.nau.edu> on Thursday,
December 30, 2004 at 3:05 PM -0500 wrote:
> Anthony, my question would be, "Why is one needed?"
>
>
> Perhaps its my perspective of continually teaching first year physics
> students, but I find that I have to threaten instant Fs for the course
> for anyone who uses a single range equation. Students come in from high
> schools so attuned to one-equation solutions to all problems in life
> that we do them a disservice, I feel, if we perpetuate that.
>
>
> I tell them that during my career in the Navy I have shot many different
> projectiles, from 45 caliber ammunition to torpedoes (armed only with
> test instrumentation, thank God), and never was my aim point at the
> same elevation as the launch point of that projectile. Thus, I never
> give a problem with equal launch and landing point elevations. They
> have to solve the vertical problem for time and then use that to solve
> the horizontal problem.
>
>
> Better to teach them multistep problem solving. This teaches them to
> organize their thoughts and to design solution approaches.
>
>
> Beyond that, one can teach them to do some simple programming on a
> spreadsheet (i.e., entering of formulae) and then how to play "what if"
> with the input parameters. This sets them up for modeling and for
> playing with their data to determine the sensitivity of results to
> uncertainties in the inputs.
>
>
> Real life is too much fun to spend it looking for easy-solution
> approaches.
>
>
> Jim
>
>
> On Thursday 2004 December 30 11:44, Anthony Lapinski wrote:
> > Neglecting air resistance, we all know that the maximum range for a
> > projectile occurs when the launch angle is 45? on level ground. But
> what
> > if the object is launched from a cliff of height H above the ground?
> Here,
> > the maximum range occurs at less than 45?. I've searched most of the
> > college texts I have, but I can't find a "range formula" that has the
> > height included. Is there such an equation with an initial height
> (similar
> > to R = v^2 sin2q/g on level ground)?
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