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After watching a news story about a fire in a high rise apartment building, you and friend decide to design an emergency escape device from the top of a building. To avoid engine failure, your friend suggest a gravitational powered elevator. The design has a large, heavy turntable (a horizontal disk that is free to rotate about its center) on teh roof with a cable wound around its edge. The free end of the cable goes horizontally to the edge of the building roof, pases over a heavy vertical pulley, and then hangs straight down. A strong wire cage which can hold 5 people is then attached to the hanging end of the cable. When people enter the cage adn release it, the cable unrolls from the turntable lowering the people as safely to the ground. to see if the design is feasible you decide to calculate the acceleration of the fully loaded elevator to make sure it is much less than g. Your friend design has the radius of the turntable disk as 1.5 m and its mass as 2x that of the fully loaded elevator. The disk which serves as the vertical pulley has 1/4 the radius of the turntable and 1/16 its mass. In your physics book you find that the moment of inertia if a disk is 1/2 that of a ring.

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