Similar to 33 second mystery #1
 

A truck is approaching a 2 mile long bridge. The weight limit for the bridge is exactly 2 tons; should the limit be exceeded by one ounce the bridge will collapse. The truck is just 2 oz shy of exceeding the weight limit with the driver. In the dead center of the two mile bridge, a 3 oz bird crashes into the grille of the truck, adding its total weight to the weight of the truck. The bridge does not collapse, why?

The truck weighs less because it had to drive to the bridge and therefore used some of its fuel. Less fuel = less weight.

Or driving along the first mile of the bridge...

The guy drove halfway across the bridge, go out, and went catch-and-release fishing. :p

Or one could be assuming that the truck was directly over a set of pilings when the bird hit it.

It has to be the gas. The truck would have consumed more than 1oz of fuel during the first mile of the bridge.

maybe the bird just grabbed on with its feet and continued to flap its wings, thereby making the truck even lighter... or maybe not. whatever

the truck is actually an intergalactic freighter travelling at light speed so the moment it gets to the bridge it's off of the bridge.

BTW, the little birdie disintegrates into powder, so it actually adds no additional weight to the truck in this scenario.

Maybe the truck is creating lift.

The bird bounced off.

The bird would have deflected upwards, thus actually reducing the downward foxe of the lorry on the bridge. The bird then goes splat and falls off, as the lorry is rebounding down again, and falls off before the forces return downwars, so the total weight never actually goes above the maximum.

I'm almost positive that this is the correct answer.

Actually... the weight of the bird is insignificant... the force created by the impact is distributed equally throughout the grill (which is what they are designed to do) and is therefore displaced... only adding maybe an ounce to the truck if that...

Stupid bird.

The Driver ate some bad chicken before he got on the road. Just before he got to the bridge, he barfed out the window, therefore reducing the weight, so the bird had no effect.

Because before getting onto the bridge, the driver filled balloons with the helium he was freighting, and attached them to the truck.

This is another one of those questions that's more a guessing game than anything else.