Question 92534
Boat builders share an old rule of thumb for sailboats. The maximum speed K in knots is 1.35 times the square root of the length L in feet of the boat's waterline.
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a. A customer is planning to order a sailboat with maximum speed of 8 knots.
How long should the waterline be?
:
1.35 * Sqrt(L) = K
1.35 * Sqrt(L) = 8
Sqrt(L) = 8/1.35; divide both sides by 1.35
Sqrt(L) = 5.9259
(Sqrt(L))^2 = 5.9259^2; square both side
L = 35.1 ft at the waterline
:
Check on calc: 1.35*Sqrt(35.1) = 7.998 ~ 8
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b. How much longer would the waterline have to be achieve a maximum speed of 10 knots?
Do the same here
1.35* Sqrt(L) = 10
Sqrt(L) = 10/1.35
L = (10/1.35)^2
L = 54.9 ft at the waterline
:
54.9 - 35.1 = 19.8 ft longer to raise the speed to 10 knots
:
Check it the same way: 1.35 * sqrt(54.9)
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