Guest Posted November 4, 2007 Report Share Posted November 4, 2007 A large truck weighing 3 tons is driving on a long bridge that has a weight limit of exactly 3 tons. When the truck is halfway across the bridge, a crow lands on top of the truck. But the truck still does not exeed the limit and makes it safely across. How can this be?? Quote Link to comment Share on other sites More sharing options...
0 bonanova Posted November 4, 2007 Report Share Posted November 4, 2007 He lands lightly and tangentially, just touching the tips of his claws to the truck. He then glides on a horizontal path, his outspread wings bearing all his weight. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted November 4, 2007 Report Share Posted November 4, 2007 well, Newtons third law wouldn't allow that. The force of the air pushing down would be opposite and equal to the weight of the bird. If no one figures it out I'll put out the spoiler Quote Link to comment Share on other sites More sharing options...
0 Guest Posted November 4, 2007 Report Share Posted November 4, 2007 ahh wat the heck When the truck gets halfway across the bridge, it has used up some of its gas. It's a long bridge so he loses enough gas to compensate for the weight of a crow. w00t Quote Link to comment Share on other sites More sharing options...
0 bonanova Posted November 4, 2007 Report Share Posted November 4, 2007 I'd love to hear your solution. But consider this, regarding mine. You're claiming the crow would be supported by increased pressure [born by the truck - generalization of Newton's 3rd law] on the bottom of its wings. But it's not Newton's 3rd law that supports a crow in flight. It's Bernoulli's principle. The air speed is greater, and the pressure is less, on the top of the wing. So normal atmospheric pressure exists beneath its wing, and no weight is added to the truck's axles. Here's a thought experiment. Attach the crow to the truck with a short rubber band. Tell the crow to "press down" on the truck using maximum wing force. Does the rubber band not stretch? Thereby decreasing the truck's force on the bridge? Quote Link to comment Share on other sites More sharing options...
0 bonanova Posted November 4, 2007 Report Share Posted November 4, 2007 I'll see your Newton's Third Law and raise you a Solar Powered Truck! Gas ........? What gas? Good one. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted November 5, 2007 Report Share Posted November 5, 2007 dude, you totally crushed my dreams with your pessimistic attitude. cheers Quote Link to comment Share on other sites More sharing options...
0 bonanova Posted November 5, 2007 Report Share Posted November 5, 2007 Amends ... have one on me. http://tbn0.google.com/images?q=tbn:AeD0ew...egalbeermug.jpg Quote Link to comment Share on other sites More sharing options...
0 Guest Posted November 5, 2007 Report Share Posted November 5, 2007 yippee! Quote Link to comment Share on other sites More sharing options...
0 Guest Posted November 6, 2007 Report Share Posted November 6, 2007 I've been reading the forums here for a while but only just joined recently. Anyway, I know this isn't the answer you were looking for but one thing about engineering and safety and bridges is that they have a margin of safety when designing and building them. A 3 ton bridge will probably hold 4.5 tons safely yet only be rated for 3 tons so that the 4.5 tons never gets approached and pushes the limits of the bridge. So a crow will not weight 1.5 tons and therefore be able to sit on a 3 ton truck without the bridge breaking Quote Link to comment Share on other sites More sharing options...
0 Guest Posted November 6, 2007 Report Share Posted November 6, 2007 yeah, I knew someone would say that after at least a few "bridge crossing" riddles. I was thinking the same thing myself when I wrote it. I guess for the sake of a riddle you must just go by what it says. But points for originality Quote Link to comment Share on other sites More sharing options...
0 Guest Posted December 21, 2009 Report Share Posted December 21, 2009 He picks up his cup of coffee right as the crow lands on his truck. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted December 31, 2009 Report Share Posted December 31, 2009 brige is not a line and this can be kust becouse of centrifugal force? Quote Link to comment Share on other sites More sharing options...
0 Guest Posted December 31, 2009 Report Share Posted December 31, 2009 He picks up his cup of coffee right as the crow lands on his truck. This is very wrong idea. It this case, even without the crow weight of truck should increase. Quote Link to comment Share on other sites More sharing options...
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A large truck weighing 3 tons is driving on a long bridge that has a weight limit of exactly 3 tons.
When the truck is halfway across the bridge, a crow lands on top of the truck.
But the truck still does not exeed the limit and makes it safely across.
How can this be??
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