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Unformatted text preview: roofner (bar784) Homework 6 Weathers (17104) 1 This printout should have 10 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points Joe pushes down the length of the handle of a(n) 10 . 7 kg lawn spreader. The handle makes an angle of 46 . 3 with the horizontal. Joe wishes to accelerate the spreader from rest to 1 . 34 m / s in 1 . 3 s. What force must Joe apply to the handle? Correct answer: 15 . 964 N. Explanation: The horizontal component of the force is F h = F cos . Let v be the final velocity of the spreader. According to Newtons second law, F h = ma h so F cos = m v h t F = m v h t cos = mv t cos = (10 . 7 kg) (1 . 34 m / s) (1 . 3 s) cos 46 . 3 = 15 . 964 N 002 10.0 points A 63 kg boy and a 36 kg girl use an elastic rope while engaged in a tugofwar on a frictionless icy surface. If the acceleration of the girl toward the boy is 2 . 8 m / s 2 , determine the magnitude of the acceleration of the boy toward the girl. Correct answer: 1 . 6 m / s 2 . Explanation: According to Newtons Third Law of Mo tion the force the boy exerts on the girl is the same as the force the girl exerts on the boy, so F g = F b m g a g = m b a b a b = m g a g m b 003 (part 1 of 2) 10.0 points An object in equilibrium has three forces ex erted on it. A(n) 34 N force acts at 67 . 9 , and a(n) 54 N force acts at 31 . 6 . What is the direction of the third force? (Consider all angles to be measured counter clockwise from the positive xaxis.) Correct answer: 225 . 489 . Explanation: Basic Concepts: Choose a coordinate system with the pos itive xaxis representing 0 and the positive yaxis representing 90 . Any force F has an xcomponent of F x = F cos and a ycomponent of F y = F sin where is measured from the xaxis. Solution: Since F 1 and F 2 act up and to the right, the force F must act down and to the left, so F lies in the third quadrant....
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 Fall '08
 Weathers
 mechanics, Work

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