What is the formula for the curve made when you bend a stiff card by pressing inwards at the edge between your fingers? Show your derivation or proof.
The bridge in the photo is made from two steel cables, overlaid with redwood 2 by 6 lumber. The bridge is 110 feet long, and sags in the middle 5 feet lower than the ends. There is 400 pounds of wood. The cables are rated at 2,000 pounds each.
How much extra weight can the bridge support? Show the formula, and the derivation or proof. How does allowing extra sag affect the result? What if four cables were used?
Nyles Bauer (EE, ABE, AME, MBIM) University of Arizona
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