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Unformatted text preview: Nguyen, Thanh – Homework 6 – Due: Sep 21 2007, 7:00 pm – Inst: D Weathers 1 This printout should have 10 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points Joe pushes down the length of the handle of a(n) 10 kg lawn spreader. The handle makes an angle of 41 . 3 ◦ with the horizontal. Joe wishes to accelerate the spreader from rest to 1 . 34 m / s in 1 . 7 s. What force must Joe apply to the handle? Correct answer: 10 . 4921 N. Explanation: The horizontal component of the force is F h = F cos θ. Let v be the final velocity of the spreader. According to Newton’s second law, F h = m a h so F cos θ = m Δ v h Δ t F = m Δ v h Δ t cos θ = m v t cos θ = (10 kg) (1 . 34 m / s) (1 . 7 s) cos 41 . 3 ◦ = 10 . 4921 N keywords: 002 (part 1 of 1) 10 points A 56 kg boy and a 35 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 3 . 3 m / s 2 , determine the magnitude of the acceleration of the boy toward the girl. Correct answer: 2 . 0625 m / s 2 . Explanation: According to Newton’s 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 keywords: 003 (part 1 of 2) 10 points An object in equilibrium has three forces ex erted on it. A(n) 20 N force acts at 61 ◦ , and a(n) 50 N force acts at 57 . 1 ◦ . What is the direction of the third force? (Consider all angles to be measured counter clockwise from the positive xaxis.) Correct answer: 238 . 214 ◦ . 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 θ and a ycomponent of F y = F sin θ where θ is measured from the xaxis....
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This note was uploaded on 10/24/2011 for the course PHYS 1710 taught by Professor Weathers during the Winter '08 term at North Texas.
 Winter '08
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