Ask a Question
or
Create a Poll
  1. Home /
  2. Questions /
  3. Science
  4. / Engineering
  5. / Civil Engineering
  6. / Bridge Engineering

by agent1337 on March 17th, 2007

agent1337

Question

Help answer this question below.

A bridge 3 miles long with a maximum weight capacity of 10,000LBs (anything over will make it collapse.) a truck that weighs exactly 10,000LB drives accross and when it reaches the middle a bird weighing 20 grams lands on it. Why didnt the bridge collapse

  • Like
  • Report
Share:
Other

Answers. 9 helpful answers below.

  • by mejinn on March 17th, 2007

    mejinn

    My only guess is that the truck had already burned enough fuel by the time it reached the middle of the bridge therefore reducing the truck's weight and able to support the 20g bird.

    • Like
    • Report

    1 comment | Post one | Permalink

  • by Esteban-- Smart ass Pumpkin on March 17th, 2007

    Esteban-- Smart ass Pumpkin

    because at the contact points, the 4, 6 or 8 tires the weight is distributed between them. and truck are notorious for lying about their weight

    • Like
    • Report

    No comments. Post one | Permalink

  • by swannie on March 17th, 2007

    swannie

    because the whole bridge (3 mi.) can withstand 10000lbs, but the truck is only in one place. if the truck filled up the whole 3 miles, then the bridge would collapse once the bird landed on it.

    • Like
    • Report

    No comments. Post one | Permalink

  • by moffattn on November 24th, 2008

    moffattn

    Only a manufacturer will answer your question...http://www.moffattnichol.com/practices_transportation.php

    • Like
    • Report

    No comments. Post one | Permalink

  • by Marks_A_Lot on August 25th, 2009

    Marks_A_Lot

    The truck passes over each pier. Each pier is rated for 10,000 lbs. Once in the middle the truck is only giving 5,000 lb load on each pier. The bird didn't matter as long as it gets off before reaching the next pier.

    The classical lever problem... the weight at each end is determined by the force x distance from the support point.... so the span of 3 miles when the truck is over pier "A" it supports the 100% of the truck .. pier "B" nothing ... as the truck moves to the next pier say 1/3 the distance the force is 2/3 x 10,000 = 6,666 lbs Pier A and 1/3 x 10,000 lbs = 3,333 Pier B... at the halway point they support 5,000 lbs each as the truck is 2/3rd's the distance to Pier B then Pier A supports only 3,333 and pier b 6,666 and when over pier B pier a supports nothing and pier b 10,000 ...

    • Like
    • Report

    No comments. Post one | Permalink

  • by shahzi on May 15th, 2009

    shahzi

    It don't seems to be a scientific question, is it just a riddle. These parameters are not enough. Its answers could be something like "mejinn" told

    "My only guess is that the truck had already burned enough fuel by the time it reached the middle of the bridge therefore reducing the truck's weight and able to support the 20g bird"

    • Like
    • Report

    No comments. Post one | Permalink

  • by Russ on July 30th, 2009

    Russ

    Possibly the design of the truck chasis is such that when it travels at a certain rate of speed it becomes lighter due to the aerodynamic lift being created.
    Ocean liners travel higher in the water when at speed than they do when going slow.

    • Like
    • Report

    No comments. Post one | Permalink

  • by anwo247 on March 28th, 2009

    anwo247

    A truck definitely is not up to 3 miles length. Let us say the truck is about 20feet long for example. So if this bridge should even sustain it at all, then, the bridge was designed up to the strength of 10,000lBS per 20 feet. Therefore if this is the max design, then the total bridge is more than 10,000LBS per 3 miles.

    The argument here is that, when the truck is not as long as 3mile, which for sure we know, then, a 10,000LBs per 3 mile bridge will not sustain a truck of less length that weighs 10,000LBS. forget about the bird, because the bridge would have collapsed before the bird gets there!

    Mind you that the concentration of the truck weight towards the center increases the moment depending on the location of piers or unsuported span which you did not state in the question. "Moment capacity is a function of unbraced length"

    • Like
    • Report

    No comments. Post one | Permalink

  • by ostriches on December 18th, 2010

    ostriches

    The bridge has a capacity measure in weight, not mass. The weight on the bridge is the force exerted on it by gravity acting on a mass. When the truck passes over the apex of the bridge, it is travelling forward, but also slightly upward. This slight force along the positive Y-axis counters at least 20 grams of downwards force by gravity.

    This is the same 'weightless' effect you feel when a roller coaster goes over the top of a climb, or when a car goes over a hill with great enough speed. The opposite can be felt at the bottom of hills, when you are pressed into your seat.

    This is all elementary force vector physics, and would be fair game in any high-school level physics course. All previous answers include extraneous information, making their answers into solutions to a riddle, and not a basic physics question.

    1 comment | Post one | Permalink

Want to attach an image to your answer? Click here.

Did this answer your question? If not, then ask a new question or create a poll.

More Questions. Additional questions in this category.

You're reading A bridge 3 miles long with a maximum weight capacity of 10,000LBs (anything over will make it collapse.) a truck that weighs exactly 10,000LB drives accross and when it reaches the middle a bird weighing 20 grams lands on it. Why didnt the bridge collapse

Follow us on Facebook!

Related Ads

Related Questions

Professionally Researched

ANSWERBAG BUZZ

What is the maximum weight a bridge can hold
3 miles long
Maximum bridge capacity
A truck that weighs exactly 10000
What is the maximum weight that the confederation bridge hold

Answerbag

a Demand Media company