MIDTERM_02_REVIEW_01_solution

# MIDTERM_02_REVIEW_01_solution - Version 001 MIDTERM 02...

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Version 001 – MIDTERM 02 REVIEW I – turner – (56910) 1 This print-out should have 15 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. FrictionOnAMovingBlockTest2Q 001 (part 1 of 2) 10.0 points A block oF mass M is pulled on a horizontal plane by a Force oF magnitude F that makes an angle θ ( θ > 0) with respect to the horizontal surFace. The coe±cient oF kinetic Friction For the surFace is µ . What is the Force oF Friction experienced by the block? 1. µ ( M g + F cos θ ) 2. µM g 3. F µM g 4. µ ( M g cos θ + F ) 5. µ ( M g F cos θ ) 6. µ ( M g F sin θ ) correct 7. µ ( F + mg ) Explanation: ²rom the Free-body diagram oF the block, the net vertical Force is zero, so N + F sin θ = M g, or, N = M g F sin θ, which implies that F friction = µN = µ ( M g F sin θ ) . 002 (part 2 of 2) 10.0 points IF the magnitude oF the Force v F is initially zero and is then slowly increased, keeping the angle θ fxed, what is the value oF F at which the block loses contact with the surFace? 1. F = M g cos θ 2. F = M g tan θ 3. F = M g sin θ correct 4. F = µMg 5. F = M g sin θ 6. F = M g tan θ 7. F = M g cos θ 8. F = µM g cos θ Explanation: The block will lose contact when N = 0, which happens when F = M g sin θ . Concept 13 27 003 10.0 points A piece oF iron is Fastened on top oF a block oF wood ³oating in water. IF the block is inverted so the iron is below the block oF wood, would the wood ³oat at the same level, lower, or higher? 1. It depends on the ratio oF iron and wood volumes. 2. Higher, because there is a buoyant Force acting on the iron now. correct 3. It would ³oat lower, because the iron displaces water and the overall water level would rise. 4. It would ³oat at the same level. Explanation:

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Version 001 – MIDTERM 02 REVIEW I – turner – (56910) 2 The iron-wood unit displaces its combined weight and the same volume of water whether the iron is on top or the bottom. When the iron is on top, more wood is in the water. When the iron is on the bottom, less wood is in the water. U-235 and U-238 004 10.0 points Consider following statements which compare U 235 medium with U 238 medium based on the ball-spring model. Which of the following statements are correct? On the length of the interatomic bonds: Ia. d 235 < d 238 Ib. d 235 = d 238 On the stiFness of the interactomic bonds: IIa. k 235 > k 238 IIb. k 235 = k 238 On the speeds of sound: De±ne the ratio R = v 235 v 238 IIIa. R = r 238 235 IIIb. R = r 235 238 1. Ia, IIa, IIIa 2. Ia, IIa, IIIb 3. Ia, IIb, IIIa 4. Ib, IIb, IIIa correct 5. Ib, IIa, IIIa 6. Ia, IIb, IIIb 7. Ib, IIb, IIIb 8. Ib, IIa, IIIb Explanation: U 238 contains 3 more neutrons than U 235 . So far as the electric content of the two atoms
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## This note was uploaded on 03/20/2012 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas.

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MIDTERM_02_REVIEW_01_solution - Version 001 MIDTERM 02...

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