Thursday, February 07, 2008

An engineering puzzle

Lost a lot of working time over the last two days involved in depressing but confidential duties that I'm not allowed to explain. ( That what comes of volunteering for anything ). No time for the usual blast at the evil of socialism today - unless they do something really stupid before 5pm. Instead let me leave you with an Engineering question a friend sent yesterday. If your not an Engineer have a brief think about it then skip to the answer - that what the rest of us have done straight away ;-).

ENGINEERING PHYSICS CALCULATION ( As not appearing in Ed Ball's Mc'A'Levels )

Problem: A backhoe (American for mechanical digger I suspect) weighing 18 tons is on top of a flatbed trailer heading east on Interstate 70 near Hays, Kansas. The boom and dipper stick is made of 80,000 psi high strength steel and the approaching overpass is made of 4,000 psi concrete, reinforced with 2 layers of 1 inch steel rebar spaced 6 inches each way in both the road deck and bottom of the box-beam bridge section.
Solve: When the boom and dipper hits the overpass, how fast does the trailer with the backhoe have to be going to slice the bridge in half? (Assume no headwind and no braking by the driver who is oblivious of the situation . . . )
Extra Credit: Solve for the time and distance required for the entire rig to come to a complete stop after hitting the overpass at the speed calculated above .

Answer here.

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