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Unformatted text preview: roofner (bar784) Homework 6 Weathers (17104) 1 This print-out should have 10 questions. Multiple-choice 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 tug-of-war 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 x-axis.) Correct answer: 225 . 489 . Explanation: Basic Concepts: Choose a coordinate system with the pos- itive x-axis representing 0 and the positive y-axis representing 90 . Any force F has an x-component of F x = F cos and a y-component of F y = F sin where is measured from the x-axis. 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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