1. Attachments are working again! Check out this thread for more details and to report any other bugs.

ENGINEERING QUIZ

Discussion in 'Fred's House of Pancakes' started by hycamguy07, Feb 10, 2007.

  1. hycamguy07

    hycamguy07 New Member

    Joined:
    Feb 18, 2006
    2,707
    3
    0
    Location:
    Central Florida
    Vehicle:
    2007 Prius
    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.

    Good luck :)
     
    #1 hycamguy07, Feb 10, 2007
  2. priusenvy

    priusenvy Senior Member

    Joined:
    Mar 15, 2004
    1,765
    14
    0
    Location:
    Silicon Valley, CA
    Vehicle:
    2005 Prius
    #2 priusenvy, Feb 10, 2007
  3. Bill Merchant

    Bill Merchant absit invidia

    Joined:
    May 3, 2005
    4,096
    82
    13
    Location:
    USA | Oregon | Portland area | 97004 |
    Vehicle:
    2007 Prius
    You're really up to speed, so to speak, priusguy04. That happened a year ago. The haul driver had been given a specific route, but he knew better...
     
    #3 Bill Merchant, Feb 10, 2007
  4. daniel

    daniel Cat Lovers Against the Bomb

    Joined:
    Feb 25, 2004
    14,487
    1,518
    0
    Location:
    Spokane, WA
    Vehicle:
    2004 Prius
    Impressive!
     
    #4 daniel, Feb 10, 2007
  5. Wildkow

    Wildkow New Member

    Joined:
    Jan 24, 2006
    5,270
    37
    36
    Vehicle:
    2006 Prius
    That could have been ten years ago and it's still impressive. Nice find PG04, notice that the boom did not cut through the leading edge of the bridge. That's weird! I would think that the weight of the package would play a big part in how fast they would have to be going to cause that much damage.

    Wildkow
     
    #5 Wildkow, Feb 10, 2007
  6. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
    Staff Member

    Joined:
    May 11, 2004
    14,816
    2,498
    66
    Location:
    Far-North Chicagoland
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    When I was living in Ireland, they showed me footage of lauries intentionally driven into bridges and other overpasses. The government did this to remind the drivers what will happen if they do it themselves.
     
    #6 TonyPSchaefer, Feb 10, 2007
  7. priusenvy

    priusenvy Senior Member

    Joined:
    Mar 15, 2004
    1,765
    14
    0
    Location:
    Silicon Valley, CA
    Vehicle:
    2005 Prius
    If you like those kinds of pictures, look at these:

    http://www.micom.net/oops/

    The backhoe was going from right to left in that picture, and the boom was pointed towards the front (left). That's why the railing wasn't hit, but as the boom was pushed upright, it extended until it was higher than the railing (after punching a hole through the overpass).
     
    #7 priusenvy, Feb 11, 2007
  8. daniel

    daniel Cat Lovers Against the Bomb

    Joined:
    Feb 25, 2004
    14,487
    1,518
    0
    Location:
    Spokane, WA
    Vehicle:
    2004 Prius
    :D :D :D From the above list:
    Titled "African Preflight." There's not a lot of shade in some parts of Africa, and in the hottest part of the day, the kitty cats like to rest in the shade. I was in planes that size and smaller in Kenya, but I never saw lions at the airport.

    [attachmentid=6536]
     
    #8 daniel, Feb 11, 2007
  9. koa

    koa Active Member

    Joined:
    Aug 9, 2005
    980
    45
    0
    Location:
    Hawaii
    Vehicle:
    2006 Prius
    #9 koa, Feb 11, 2007
  10. eagle33199

    eagle33199 Platinum Member

    Joined:
    Mar 2, 2006
    5,122
    268
    0
    Location:
    Minnesota
    Vehicle:
    2015 Prius v wagon
    Model:
    Two
    As someone eluded to above, the question isn't one of speed - it's one of mass and momentum. Something with a huge mass and very little speed still has a lot of momentum, and could slice through a bridge no problem... likewise, something with very little mass and high speed could slice through the bridge.

    Take, for example, a bullet and a wrecking ball. Fire a bullet into a brick wall, it might penetrate an inch... take a wrecking ball, traveling at a much slower speed than the bullet, and it'll punch right through the wall.


    So we really need some more information to answer to originally posed question - what was the mass of the truck? How wide was the bridge? How thick was the bridge?

    Yes, i'm an engineer. Not a mechanical, structural, or civil engineer, so i don't know exactly how to go about solving the question... but i do know enough to ask more questions in return :)
     
    #10 eagle33199, Feb 12, 2007
(You must log in or sign up to post here.)