Beam me up, Scotty, we’re going to need the buzz saw
Tristan and Layla are designing a beam for a footbridge.
They want minimum sag ( δ min ) at the middle of the bridge when it’s loaded.
They are ripping a round log into a rectangular beam or rectangular prism.
The beam will have a length L of 14 feet, a height of H and a width of W.
After debarking, the round log will have a diameter D of 14 inches.
Sag ( δ ) at the middle of the beam is computed by the formula:
δ = PL 3 / ( 48 E I )
Where P is the load applied, E is the Modulus of Elasticity and I is the Moment of Inertia given by the equation:
I = WH 3 / 12
Find the width W and height H of the ideal rectangular section of their beam.
W = ______ inches H = ______ inches
First correct answer to arrive at [email protected] wins a gift card worth much ice cream at Tucker’s Ice Cream of Alameda.
The correct answer to last week’s puzzle was Area A = 101824 square meters. Last week’s winner was John Lovato.
Jeff Smith is a former Math teacher and a retired US Navy Lieutenant Commander. Reach him at [email protected].
