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QUESTION:A Backhoe weighing 8 tons is on top of a flatbed trailer and heading east on
Interstate 70 near Hays, Kansas. The extended shovel arm is made of hardened
refined steel and the approaching overpass is made of commercial-grade
concrete, reinforced with 1 1/2 inch steel rebar spaced at 6 inch intervals
in a crisscross pattern layered at 1 foot vertical spacing.
Solve: When the shovel arm hits the overpass, how fast do you have to be
going to slice the bridge in half? (Assume no effect for headwind and no
braking by the driver...)
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 - check your results using the 3 attached photos
Photos here: http://www.tnab.net/backhoe/default.htm
I'd love to hear the whole story behind this mess!
ANSWER: Lots more pics at
http://www.tractorshed.com/cgi-bin/gallery/trouble_view.cgi?w=trouble
search on Hundai
If you click on 'Comments' you can see lots of commentary
The driver had just gotten on to the interstate about a mile back, got
it up to 65-70mph, this was the first bridge on his route. He was
traveling with the boom forward, the leading edge caught the bottom of
the bridge, gives you the slot you see in the one picture. Must have
been some sort of bounce when the trailer went down, allowed the boom to
poke a second hole in the bridge and come to a stop. The boom has been
peeled back, is over the back end of the excavator.
I might add that the rig weighs much more than 8 tons. The trailer alone
comes in at 8 to 10 tons, I think that excavator runs around 40,000 pounds.
http://www.free-tractor-manuals.com/equipment/mini_excavators/hyundai...
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