WHAT’S GOING ON?
Sound has a relatively low speed through air,
which means you can measure it if you have an
open space large enough. Sound travels at
344 m per second in dry air at 20 °C. This may
vary at different temperatures, but not by
much, so this experiment works pretty well just
about anywhere.
When the sound of the hammer once again
coincides with the 1 second beat, you are ready to
measure the speed of sound. Stop walking away
at this point and measure the distance between
you and the helper. You should be 344 m away,
or very close to that.
Of course, very few of us have such long gardens,
and finding a flat, open space of that length,
unless you live near a beach, may prove
troublesome. Then there will be the problem of
outside noises interfering with you detecting the
beat of the hammer. If this is the case, ask your
helper to increase the frequency of the beats to
once every half second (in which case you should
find yourself about 172 m from your helper when
the beats again coincide with the sound), or once
every quarter second if they can (when you’ll be
about 86 m away).GET
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