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Unformatted text preview: Version 045/AACDB quiz10-10 Demkov (59910) 1 This print-out should have 8 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Pretend you are on a planet similar to Earth where the acceleration of gravity is approxi- mately 10 m / s 2 . The coefficient of kinetic friction between the plane and the block is 0 . 4. A block of mass 50 kg lies on an inclined plane, as shown below. The horizontal and vertical supports for the plane have lengths of 48 m and 14 m, respectively. 5 k g = . 4 F 48 m 14m The magnitude of the force vector F necessary to pull the block up the plane with constant speed is most nearly 1. bardbl vector F bardbl 148 N 2. bardbl vector F bardbl 142 N 3. bardbl vector F bardbl 74 N 4. bardbl vector F bardbl 126 N 5. bardbl vector F bardbl 170 N 6. bardbl vector F bardbl 190 N 7. bardbl vector F bardbl 332 N correct 8. bardbl vector F bardbl 108 N 9. bardbl vector F bardbl 392 N 10. bardbl vector F bardbl 114 N Explanation: Let : x = 48 m , y = 14 m , m = 50 kg , g 10 m / s 2 , and a = 0 m / s 2 . s x y s = radicalbig x 2 + y 2 = radicalBig (48 m) 2 + (14 m) 2 = 50 m , sin = y s = 14 50 , and cos = x s = 48 50 . Consider the free body diagram for the block m g s in N = m g c o s N F mg Parallel to the ramp, F net = F g bardbl + F k F = ma = 0 , F g bardbl = mg sin , F k = k N , so F = F g bardbl + F k . (1) Perpendicular to the ramp, F net = N F g = 0 , so N = mg cos . (2) Using Eqs. 1 and 2, parallel to the ramp, we have F = F g bardbl + F k = mg (sin + k cos ) = (50 kg) (10 m / s 2 ) bracketleftbigg 14 50 + (0 . 4) 48 50 bracketrightbigg = 332 N . Version 045/AACDB quiz10-10 Demkov (59910) 2 keywords: 002 10.0 points Two identical massless springs are hung from a horizontal support. A block of mass 1 . 5 kg is suspended from the pair of springs, as shown. The acceleration of gravity is 9 . 8 m / s 2 ....
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- Spring '07