[PLUG] OT: Recommended Web Sites for Middle School Science Questions

Bill Barry bill at billbarry.org
Sun Aug 5 21:37:57 UTC 2007


On 8/5/07, Richard C. Steffens <rsteff at comcast.net> wrote:
> Can any recommend some good web sites to send an inquisitive middle
> schooler to? On his own, he came up with the question of whether a
> marble you throw in the car travels only as fast as you throw it, or
> does the speed of the car have any effect. He asked my sister, so I have
> until next Sunday to refine my answer, and come up with other resources
> for him.
>
> BTW, I know that the answer includes the speed of the car. I'm just
> looking for a good way to explain it to him.
>
> --

Like all the laws of physics, it is not obviously true that the marble
includes the speed of the car. For instance, it might depend on which
direction the car is going, or how fast the car is going or who knows
what.  For low car speeds it is has been experimentally confirmed  to
be true that the marble does include the speed of the car  and does
not depend on direction or speed.

While it is approximately true for marbles thrown in cars, it is not
generally true. If the car is going near the speed of light, and the
marble inside the car is thrown near the speed of light, then an
observer fixed on the ground will not see the marble in the car going
at twice the speed of light but will see a marble going under the
speed of light. These corrections are embodied in the special theory
of relativity.

I don't know about middle school explanations, but you might like this one
http://press.princeton.edu/chapters/s8112.html

Not pertaining directly to marbles thrown in cars, but there are  some
very nice demonstrations of modern physics here
http://www.colorado.edu/physics/2000/index.pl
that could be understood by a middle schooler

Bill



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