Enjoy this math problem I did!

Engineering Math Question 

Conditions:
A trackhoe weighing 22 tons is on top of a lowboy 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 1½ 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.
Yes, you can neglect friction.

( Sorry the pics did not transfer...  maybe next time! )   I\They showed a bridge almost cut in half by the raiased arm of the Back Hoe tractor! 

I couldn't solve it either......but who cares.  The pictures are great!
The driver was on his cell phone.
 

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