Waterbridge

Rivers and waterways have long served us well. From time immemorial waterway travel has been part of life. Today, many rivers are still being used to transport people and goods. I saw a few documentaries of river travel. One was on the Yangtze River in China where in certain parts where the river flows upwards, boatmen had to get down from the boat and pulled the boats. And one showed boats plying the rivers in England which serve as an alternative mode of transportation.

And this one, a waterbridge in Germany. Quite an engineering feat, this one.



It took six years to complete at a cost of 500 million euros and is 918 meters in length. This is a channel-bridge over the River Elbe and joins the former East and West Germany, as part of the unification project. It is located in the city of Magdeburg, near Berlin. The photo was taken on the day of its inauguration.

For those who appreciate engineering projects, here's a puzzle for you, armchair engineers and physicists. Did the bridge have to be designed to withstand the additional weight of ship and barge traffic, or just the weight of the water?



Scroll down to check if your answer is correct.



Answer:
It only needs to be designed to withstand the weight of the water! Why? A ship always displaces an amount of water that weighs the same as the ship, regardless of how heavily a ship may be loaded.
Remember your high school physics, and the fly in an enclosed bottle project? Similarly, the super sensitive scale proved that it didn't make any difference whether the fly was sitting on the bottom, walking up the side, or flying around. The bottle, air, and fly were a single unit of mass and always weighed the same.

Picture source unknown