LIFESCI 3J03 Lecture Notes - Lecture 5: Exercise Machine, Radium, Worm Drive
15 Sep 2016
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Life sci 3j03 lecture 5 - pulleys and gears. A grooved wheel that changes the direction of force applied by a rope or cable that passes through the groove. Assume all our pulleys are frictionless for today which means that the tension in the rope is the same on both sides of the pulley. 1st pulley: 600n tending to pull rope out of the ceiling. 2nd pulley: 3 ropes means 3:1 mechanical advantage: 800n pulling out because there are 2 ropes, you"re supporting 400, roof is supporting 400. 3rd pulley: 900n is pulling out because 3 ropes: you"re supporting 300, ceiling is supporting 600. Exercise machines use pulleys and cables to change the direction of force and to allow several different exercises to use the same weight stack. In the case of leg extension, the force can be very large and pulleys can be arranged to allow a strenuous lifting task without much weight.
