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Re: [Phys-L] Display case suggestions?

On 2012, Oct 03, , at 10:35, curtis osterhoudt wrote:

I'd like
your input on what makes an entertaining/pretty, or
educational/interesting display case demonstration

I've always been fond of having an accelerometer in the
elevator ... i.e. the canonical example of Einstein's
principle of equivalence.
-- Nowadays you can make an accelerometer and a strip-chart
recorder using an ipad plus a little bit of software.
-- If you want it to look more like old-school freshman
physics, you can construct a mechanical accelerometer.
Make it a /nice/ accelerometer, i.e. with a fast response
time and plenty of damping. A fast response time requires
that the mass not move very much (hint: scaling law) ...
which in turn requires the readout to have a lot of
mechanical advantage.


Another classic: In the lobby of the geophysics building,
there should be seismometer with a real-time readout, with
enough sensitivity that you can make the needle move by
jumping and landing hard on the floor.

That should be associated with a display of data from around
the world, so that visitors can watch earthquakes happening
in real time. There's always something happening somewhere.


If you want an /interactive/ demo, how about this: a demo
of the mass of air. Build an equal-arm balance with a
transparent bottle at each end. Thin flexible tubing runs
through the pivot and out to each bottle. A hand-operated
pump (bicycle pump) provides air pressure. Everything is
nice and symmetrical except that the tubing to one of the
bottles is blocked. The other is unblocked, so that pressure
builds up in the bottle. A pressure of two or three ATM above
ambient is plenty of mass; the balance tips. A simple ball
valve releases the pressure when desired.

In a classroom situation you can let people /feel/ the weight
of the air directly ... but this is not so easy in a "display"
situation if you want vandal-resistant unattended operation.
I can imagine a mechanism whereby the upgoing arm of the balance
picks up slack and then picks up a US nickel coin (five grams),
but I leave the details to you.