Re: [Phys-l] Student engagement--GAIN

[Brian Whatcott <betwys1@sbcglobal.net>]

This is a pleasant puzzle, dressed up for obfuscation.
Say it were presented in this manner:

John sets out to meet Sandra, who is 33 meters away.
He steps towards her at 1.5 meters/sec. She steps out
towards him at the same time, at 2.5 meters/sec.
There is a lamp post at 18 meters from John's starting
point. This post is initially 15 meters from Sandra
of course.
Where do they meet, in relation to the lamp post?
I fancy more kids could answer this algebraically.

The dressed up puzzle reminds me of the puzzle
starring an  insect flying to and from between two trains:
and how far it travels before being  squashed when
the  locos collide.   This one too, has a need
to be 'unfolded' for ready solution.

Brian W
p.s. This is not to minimize the conceptual visualization
value of the graphical approach over the algebraic method
for the puzzle as given.

John Clement wrote:
> /snip/
> Here is a specific problem that students in general either find impossible
> to do, or impossible in a short time to do by algebra. /snip/
> http://srri.umass.edu/files/mop_samples/Act016.pdf /snip/
John M. Clement   Houston, TX

>   
> > > Actually there are some problems which  are very difficult using equations, and are much easier using either graphs or motion maps.