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Thread: Joint Variation

20131002, 12:25 #1
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Joint Variation
This one puzzles me. I thought I knew how to do that, but my answer didn't agree with the provided answer (no explanation, however). I can't justify the "correct" answer.
Let's see what others think.

20131002, 14:42 #2
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Well, if it varies as the square of the wind velocity and the wind velocity triples then the force should be 9 times (3 squared) or 405 pounds, since the sail area is constant.
Of course, to some of us 405 pounds might be the cost
What was the "correct" answer?

20131002, 16:51 #3
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I read it as varying as the AREA OF THE SAIL and the SQUARE OF THE VELOCITY. While I agree that the square is 9, as you pointed out, I thought the 9 should be multiplied by the area of the sail. Yes, your answer was the one they said was correct. But I don't understand why you wouldn't multiply the 9 times the 50 (area of the sail).

20131003, 22:09 #4
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KW,
I would have done the same calculation as Jockmullin. If the wind velocity increases by a factor of 3 then the pounds would increase by a factor of 3 squared. I believe that you might have made the assumption that: sail size x wind velocity= the pressure on the sail. It is probably some intense formula that involves many variables such as the angle of the wind to the sail, resistance, direction of current, etc., however, if all of these factors are constant, then pounds would be directly proportional to wind velocity.
I am just surprised that it was not measures in something like pounds per square foot.
Not a sailor, more a landlubber.Last edited by Maudibe; 20131004 at 17:36.