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Unformatted text preview: November 28, 2007 PHY2053 Quiz 9 (Chapter 9.1-9.8) Name: UFID: 1. (5 pts) A steel cable 1.50 m long and 3 10&#6; m in cross sectional area hangs from the ceiling of an elevator and 800-kg mass is attached the end of the cable. The cable is stretched by 2.50 mm when the elevator is accelerating upward. Find the acceleration of the elevator. (Youngs modulus of steel is 20 10 Pa.) The tension in the cable is given by F = AY(L/L) = 3 10&#6; 20 10 (2.5 10/1.5) = 10000 N Applying the Newtons second law to the mass, we get, ma = F-mg a = (F-mg)/m = (10000-800 9.8)/800 = 2.70 m/s 2. (5 pts) A light spring with a spring constant of 150 N/m rests vertically on the bottom of a beaker of water (density = 1000 kg/m). A 3.00 kg aluminum block (density = 2700 of a beaker of water (density = 1000 kg/m)....
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