quiz10-10-solutions

# quiz10-10-solutions - Version 045/AACDB quiz10-10...

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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 – fnd 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 coe±cient 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. 50 kg μ = 0 . 4 F 48 m 14 m The magnitude oF the Force v F necessary to pull the block up the plane with constant speed is most nearly 1. b v F b ≈ 148 N 2. b v F b ≈ 142 N 3. b v F b ≈ 74 N 4. b v F b ≈ 126 N 5. b v F b ≈ 170 N 6. b v F b ≈ 190 N 7. b v F b ≈ 332 N correct 8. b v F b ≈ 108 N 9. b v F b ≈ 392 N 10. b v F b ≈ 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 θ x y s = r x 2 + y 2 = R (48 m) 2 + (14 m) 2 = 50 m , sin θ = y s = 14 50 , and cos θ = x s = 48 50 . Consider the Free body diagram For the block mg sin θ N = cos μN Parallel to the ramp, F net = F g b + F k F = ma = 0 , F g b = sin θ , F k = μ k N , so F = F g b + F k . (1) Perpendicular to the ramp, F net = N F g = 0 , so N = cos θ . (2) Using Eqs. 1 and 2, parallel to the ramp, we have F = F g b + F k = (sin θ + μ k cos θ ) = (50 kg) (10 m / s 2 ) b 14 50 + (0 . 4) 48 50 B = 332 N .

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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 . k k 1 . 5 kg When the block is in equilibrium, each spring is stretched an additional 0 . 13 m. The force constant of each spring is most nearly 1. k 31 N / m 2. k 74 N / m 3. k 57 N / m correct 4. k 65 N / m 5. k 19 N / m 6. k 47 N / m 7. k 58 N / m 8. k 98 N / m 9. k 16 N / m 10. k 140 N / m Explanation: Let : m = 1 . 5 kg , x = 0 . 13 m , and g = 9 . 8 m / s 2 .
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quiz10-10-solutions - Version 045/AACDB quiz10-10...

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