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RE: [RC] Physics - heidiSure it does, Bruce. But given the mechanical advantage of the
dolly, she CAN move twice as much with only a little bit more
work. That's the POINT. Heck, I can move a
refrigerator on a dolly, and I can't even pick one up. Which
means that given a mechanical advantage (such as a horse has with its
system of levers), even though the amount of work increases, the
increase is neglibible compared to the many other factors that the
horse faces at an endurance ride.
Let's say kat has to move a FW rider who tacks in at 145 lbs on her
dolly, and then she has to move you on her dolly, who by your
statements tack in at 235. Since she has to move the dolly, too
(sort of like tack), let's add in that weight. (She said it
weighed 20 lbs.) By my calculator, that's a little shy of being
55% more. But because the dolly has such a good mechanical
advanage, she can do so without expending near as much extra work as
she would have to do if she tried to pick both of you up.
In fact, she might be somewhat challenged to pick either of you up,
and likely couldn't carry either one of you very far, whereas she could
probably get both of you to the barn with ease on her dolly. And
she could probably move the refrigerator I mentioned, too, without
undue stress or strain--and it weighs a whole lot more than you do.
The fact that the design of the dolly minimizes the amount of work
done, even though there is an increase when you move more weight, is no
different from the fact that the design of the horse minimizes the
amount of work done. The POINT is that even though there is an
increase, it is minimal compared to the other things that a horse
encounters in the course of traveling over distance aerobically
carrying a rider. The POINT is that you can't just look at
x number of pounds and say "oh, this will require y more work."
You have to consider the mechanical efficiency of the device (in this
case the horse) that is doing the work.
Heidi
Kat said:
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