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Lateral Thinking Puzzle

Lateral Thinking Puzzle - 24 September

A large truck is crossing a bridge 100 mile long. The bridge can only hold 14000 lbs, which is the exact weight of the truck. The truck makes it half way across the bridge and stops. A bird lands on the truck. Does the bridge collapse? Give a reason.

1. how truck came over the bridge without driver ???

2. the truck falls as soon as it is over the bridge unless it is a drone! the weight of the driver would be greater than the 14000 lbs weight limit. if it is a drone then it shall fall down if the bird lands on it!

3. the full truck including the load, driver and the fuel weighs 14000 lbs, when truck reaches half way across the bridge the fuel is consumed and the truck's weight is decreased so the bridge will not collapse when the bird lands on the truck, unless the bird is much heavy as an ostrich.

4. the fuel is consumed as the truck has covered a distance.. and the weight of the bird is less than the weight of the fuel spent... hence the truck doesn't collapse

5. (half way the bridge) = (50 miles which requires considerable quantity of fuel) < (weight of the bird)

6. I think the fuel logic is right but what happens if bridge is inclined ,then their is no need of fuel it will move down due to its weight

7. No it does not collapse. Because it has driven a half mile - you would subtract the gas used from the total weight of the truck

8. We may begin to expect a chance of 50/50, for the bridge to either collapse or not. There are many problematic situations at play here, as well as several ambiguities that make this puzzle even more difficult and even impossible for it to have only one reason to be acceptable. If we were to take the elements of "A bird lands on the truck" we are already presented with several issues, e.g.: the weight of the bird, the speed at which it lands on the truck, the area of the truck it lands on. Some, and combinations of these, may determine a different outcome than others. Since these issues are at play, I discharge the 50/50 possibility—assuming this is a reasonable question.

Therefore, I suspect that something else is going on. My response is that it matters little to what our answer is to the question, it is our reasoning that is more important. The bridge may collapse, with or without the bird landing on it.

9. Having just seen the answer to this puzzle, I am content with my above reply and stand firm by it.

This puzzle is flawed!

Somehow the author and/or editor of this puzzle thinks the bridge can only collapse when the truck reaches about midpoint of the bridge, for it to either collapse or not.

This is of course a fallacy. If the bridge was indeed as weak as it was intended in the puzzle, then it would indeed have collapsed.

Therefore, under those circumstances; the bridge *would* collapse, *before* the bird would have landed on the truck.

10. It will not collapse, the truck successfully made it half way at the 50mile mark. In a real life situation; no doubt, there would be bumps on the bridge.

When going over a bump, any vehicle will have a change in mass caused from the springs in the tire; the vehicle will bounce upwards causing the CoM (centre of mass) to change (upwards), the mass will decrease for an instant. After the action/ movement , the CoM will come to a rest, vertically (at this point the mass = 14k lbs). Then the CoM changes again (downwards), the mass has now increased. This increase will be quite heavy since the truck is heavy itself.

Therefore we can now say; Mass of Truck + Bird > Mass of Truck + extra weight added on from the bump.

1. Ya true....You are quite logical.....

11. No, it wont. If the truck weighs 14000lbs the driver even adds weight to it and if the bridge is so long there must be other vehicles

12. In normal case, The bridge would be collapsed due to bird's extra weight. U didn't ask how to make not to collapsethe bridge. So, it would collapse in normal case in anyway. :(

13. the weight of the bird is balanced by the alcholic liquid which was using by the driver at the time of stop

14. No no the bridge holds 14000 lbs which is the weight of the truck and the driver combined and since the truck was at the limit when the truck stoped the bird had a chance to land and since the bird has weight, the truck then exceeded the limit and broke the bridge.

15. Sack the bridge builders! What are the chances that another vehicle will not cross or already be on the bridge? At 100 miles long the driver of one vehicle could not be aware of all other possible vehicles on the bridge - which is a bit of a problem when one vehicle can exceed the weight limit. I think there may be some health and safety issues! Or am I taking the whole thing too literally? ;)

16. No, the bridge didn't collapse as after travelling half way, atleast some petrol might have been used which reduced the weight of the truck due to which it could hold the weight of the bird too.

17. How come only one truck in on the bridge? if its a public facility so there must be more vehicles right?

18. Hi,
I like your picture about thinking on Google and you might like Nemonik Thinking http://nemonik-thinking.org/ Nemonik thinking is a smarter way of thinking that will accelerate your thinking and improve your memory. It prevents mental blind spots and is easy to use. All it takes is 17 words! Dr Auke Schade.

19. I think I came up with a puzzle that disproves duality mathematically:

http://papoosedoorbelle.blogspot.com/2016/01/math-lateral.html

20. I think I came up with a puzzle that disproves duality mathematically:

http://papoosedoorbelle.blogspot.com/2016/01/math-lateral.html