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Lifting a Boat



As said in my about me post, I like sailing, and let me tell you something there is a lot of physics in the sport of sailing. To start with the basic, I am going to talk first about getting the boat in the water. Often people keep their boats on trailers and lift them into the water every time they are going for a sail. This is no simple task as the particular boat I sail weighs in the neighborhood of 3,100 lbs (1.55 US Tons).


To help with this problem there are cranes provided that we can use to lift the boat into the water that have a max weight of 2 tons.


The crane's arm is about 6m long, so with the torque equation  \tau  = rF we can find the torque put on the crane. \tau =(6m)(13789N) = 82734mN, for context if you hold a liter of water (1kg) at arms length (.5m) thats only about 4.9mN of torque on your arm. The crane does have a max weight that can be put on it, so the max torque that can be applied to the crane would be 106752mN. There are countless other things that could affect the lifting strength of the crane including the chain that leads to the hook. The max strength that this chain should hold would be about 17792N. If the equipment is not in good condition then failure can happen and you are left with a boat that is smashed on the concrete and possible personal injury (speaking with experience).

Thanks to modern technology and materials this feat of physics can be accomplished for a nice sail.


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That's really cool, I never realized how much work it takes to get some of the sail boats into the water.  What kind of equipment mostly affects the max torque of the crane? 

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