Help the Fisherman
From time to time, the homework for my PRIMES STEP students includes questions that are not exactly mathematical. Last week, we had the following physics puzzle.
Puzzle. A fisherman needed to move a heavy iron thingy from one river’s shore to another. When he put the thingy in his boat, the boat lowered so much that it wasn’t safe to operate. What should he do?
The expected answer: He should attach the thingy to the bottom of the boat. When the object is inside the boat, the boat needs to displace enough water to account for the entire weight of the boat and the thingy. When the thingy is attached to the bottom of the boat, the thingy experiences its own buoyancy. Thus, the water level rises less because the thingy displaces some water directly, reducing the boat’s need to displace extra water. Thus, the amount of weight the fisherman saves is equal to the amount of water that would fit into the shape of this thingy.
As usual, my students were more inventive. Here are some of their answers.
- The fisherman could cut the iron thingy and transport it piece by piece.
- He can swim across and drag the boat with a rope with the thingy inside.
- He can use a second boat to pull the first boat with the thingy in it.
- It is another river’s shore, so he can just take the iron with him to a different river without going over water.
- If the fisherman has extra boat material, heightening the boat’s walls would keep it from sinking.
Also, some funny answers.
- He could fast for a few days, making him lighter.
- He could tie helium balloons to the boat to keep it afloat even after he gets in.
- Wait until winter and slide the boat on ice.
And my favorite answer reminded me of a movie I recently re-watched.
- You’re gonna need a bigger boat.
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Ivan:
The fisherman should overinsure the boat and the thingy and proceed as planned.
28 September 2024, 7:02 amtanyakh:
Ivan, LOL.
28 September 2024, 10:41 am