Engineering challenge

Engineering challenge:

Do not view pictures until the quiz problem has been read.

Given:
A Backhoe weighing approximately 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, at what speed do you have to
be going to slice the bridge in half? (OK, maybe 3/4) (Assume no effect
for headwind and no braking by the driver...)

Extra Credit: Solve for the time and distance required for the entire rig
(excluding dust cloud) to come to a complete stop after hitting the overpass.

Now view pictures.