SOLUTION: the stiffness 'S' of a rectangular beam varies jointly as the width and the cube of the depth. if the stiffness is 90 when the width is 2 and the depth is 3, find the stiffness for

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Question 200514: the stiffness 'S' of a rectangular beam varies jointly as the width and the cube of the depth. if the stiffness is 90 when the width is 2 and the depth is 3, find the stiffness for a beam with a width of 5 and a depth of 2
Answer by Alan3354(69443) About Me  (Show Source):
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the stiffness 'S' of a rectangular beam varies jointly as the width and the cube of the depth. if the stiffness is 90 when the width is 2 and the depth is 3, find the stiffness for a beam with a width of 5 and a depth of 2
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S = k*w*d^3 (k is a constant)
90 = k*2*27
k = 90/54 = 5/3
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S = (5/3)*5*2^3
S = 200/3