Tease your mind,

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Rubber Balloons at the Beach

Question

On a trip to the beach, you take a rubber balloon, some string and a lead weight. You inflate the balloon with enough air so that, with string and weight attached, it will remain suspended in water at a depth of 30 feet. That is, the air-filled balloon's buoyancy is exactly balanced by gravity.

Now you pull the balloon, string and weight down to 60 feet. If you let go of the balloon at this depth, will it rise or sink? (Assume the water temperature is the same at both depths.)

 

 

 

 

 

Answer

At 60 feet, the water pressure upon the balloon is greater than at 30 feet, causing it to compress and increase in density. (The total volume of the balloon/weight system becomes smaller, but total mass remains the same.) Being denser than it was at 30 feet, the balloon sinks.

Who would have thought?

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