Resistance on snow and ice
by Theo Schmidt
illustration by Charles Snyder
December 21, 2004
HPeJ has now been going for about half a year with an article or
something on the 21st of each month and with several articles in the
queue for next year. However please
continue to send articles and information for publication! And Season's
Greetings to you all!
This being the cold, snowy season in the northern
hemisphere,
articles on ice-skating, cross-country skiing or studded tires would
seem appropriate, but: some of you readers must write them first! Or at
least send data or pictures. I would like to assemble data on the
resistance of steel blades on ice, skis on snow, and sleds on both.
Measuring these is not too difficult: you need a spring scale and a
rope for pulling a skater/skier/sled, and a bathroom scale for weighing
people or loads so that the non-dimensional coefficient similar to the
coefficient of rolling resistance can be
determined. This is simply the pulling force divided by the
force acting at a right angle to this. This so-called normal force is
approximately the weight at small slopes, or more precisely the mass in
kg times the local gravitational acceleration (about 9.8 m/s^2) times
the cosine of the slope (gives Newtons).
First, find a dead flat surface like a frozen
lake or a skating rink and experiment on different qualities of ice and
snow, also describing this quality (e.g. smooth white ice, perfect
clear ice, bumpy ice, hard snow). If you aren't sure about the slope,
do measurements in several directions. Do this at rather slow speeds
and record the speed approximately. Although sliding friction is
usually assumed to be speed-independent, in practice you will notice
some increase with pulling speed.
Or, if there is a slope and you can measure it, determine
the angle where the
skier/sled/etc. just begins to move; then the spring scale isn't
required.
Send your data by email via the contact link
below.
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