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Unformatted text preview: W done by the force F ( x ) in moving a particle from a to b to be Z b a F ( x ) dx . Problem. An electric elevator with a motor at the top has a multistrand cable weighing 2 kg/m. When the car is at the rst oor, then 60 meters of cable are paid out. When the car is at the top oor, then effectively meters are paid out. a) What is the force exerted by the motor to just lift the cable? Hint: Newtons second law says that the force is equal to mass times acceleration, F = ma , with units measured in Newtons [N=kg m/s 2 ]. You may take the free gravitational accelera-tion to be g = 10m/s 2 . b) How much work does the motor do just lifting the cable when it takes the car from the rst oor to the top?...
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This note was uploaded on 10/31/2011 for the course MATH 1910 at Cornell University (Engineering School).