Interstate ho(e)

[sigma7]

I love it when e-mails my sister forwards to me get Snopesed. This time, though, she was actually right.

A hoe 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 criss-cross 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.

Comments

[aardy.livejournal.com]

I think the boom was only a couple feet high at the instant it hit the bridge, but was pointed towards the direction of travel, and got pushed up and back as the truck bed moved further than the concrete permitted the boom to move. If you look closely, you can see that the guardrail on the overpass is still intact, even though it's lower than the height at which the boom ended up, and the hydraulic pistons at the base of the boom look to be royally bent.