Which weighs more - A bridge full of people or a bridge full of cars?
"Non Engineer" Answer: A bridge full of people.
Explanation: An average car will weigh between 3,500 and 7,000 pounds and will take up an area of roughly 150 square feet (or 8 feet wide by 18 feet long). This equates to between 25 and 50 pounds per square foot. Whereas the average person will weigh between 120 and 240 pounds and will take up an area of roughly 2 square feet (or 1 foot long by 2 feet wide). This equates to between 60 and 120 pounds per square foot. Therefore, a bridge filled with people will weigh more than a bridge filled with cars.
Commentary: Not to worry though, bridges are designed for much more than just cars and much more that an average static load spread out over its surface. Either way, you will not catch me on a bridge filled with fully loaded concrete trucks.
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