Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: a practical physics problem with pulleys



Dear Tom,

That would work if I could approch the storage spot from ground level.
Unfortunately it is ten feet in the air. I will have to have some way
to lift the canoe. I too am in a coastal community, sort of. We have
Burrard inlet on our north coast and the Fraser River on our south
coast (http://www.city.burnaby.bc.ca/tourism/burnaby.html). I live in
the center of town. Cargo net and fishnet can be found here, but
plastic snow fence is probably easier to get!

I tried my first experiment last night with eybolts only. It took three
of us to overcome the friction, and I used rope that was too short and
too small. We did get the canoe up into position, but I took it down
again overnight. The rope (braided polyester), initially fifty feet
long, had stretched to sixty feet.

It is clear that I will need to use my pulleys (which I had already
purchased) and a thicker rope. Incidentally, another peeve I've had
for a long time is the designation of rope size by circumference rather
than diameter. While I am aware that the former is conventional in the
professional community that concerns itself with rope, the latter seems
to be making inroads at Home Depot. Joe Sixpack wins in the end. Scary.

The rope I bought has no size designation. I merely says "90 lb/40.8 kg",
hard conversion with empty precision of a kind we've become used to in
Canada. The canoe weighs about eighty pounds and is supported (in this
scheme) by four ropes, but considerably larger forces were involved in
raising the canoe because of the friction in, I hope, the eyebolts.

Leigh