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Unformatted text preview: reddy (ar38357) – Tension and inclined planes – clancy – (SCI411-2) 1 This print-out should have 9 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Can an object be in mechanical equilibrium when only a single force acts on it? Explain. 1. None of these 2. No; even one force is too much. There should be no forces acting on an object. 3. No; at least one other force is needed to cancel the action of the first force. correct 4. Yes; a single force is necessary to keep the object in mechanical equilibrium. 5. Yes; the object will act back with an equal and opposite force. Explanation: The sum of the forces acting on an object in equilibrium has to equal zero. Since only a single force acts on the object, it cannot be in equilibrium. 002 (part 1 of 2) 10.0 points The wind exerts a force of 290 N North on a sailboat, while the water exerts a force of 129 N West on the sailboat. What is the magnitude of the net external force on the sailboat? Correct answer: 317 . 397 N. Explanation: Let : F x = F water = − 129 N and F y = F wind = 290 N . 290 N 129 N v Scale: 100 m θ Thus F net = radicalBig F 2 x + F 2 y = radicalBig ( − 129 N) 2 + (290 N) 2 = 317 . 397 N . 003 (part 2 of 2) 10.0 points How many degrees west of north is this net external force directed? Correct answer: 23 . 9808 ◦ . Explanation: tan θ = F x F y θ = tan − 1 parenleftbigg F x F y parenrightbigg = tan − 1 parenleftbigg − 129 N 290 N parenrightbigg = − 23 . 9808 ◦ , which is 23 . 9808 ◦ to the west of north. keywords: reddy (ar38357) – Tension and inclined planes – clancy – (SCI411-2) 2 004 10.0 points Two men decide to use their cars to pull a truck stuck in mud. They attach ropes and one pulls with a force of 982 N at an angle of 30 ◦ with respect to the direction in which...
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This note was uploaded on 11/21/2010 for the course PHYS 12231 taught by Professor Sontar during the Fall '10 term at Ill. Chicago.
- Fall '10