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Unformatted text preview: Morgan, Mena – Homework 6 – Due: Oct 17 2007, 11:00 pm – Inst: Opyrchal, H 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 An outfielder throws a 1 . 26 kg baseball at a speed of 58 m / s and an initial angle of 54 . 4 ◦ . What is the kinetic energy of the ball at the highest point of its motion? Correct answer: 718 . 167 J. Explanation: Given : m = 1 . 26 kg , θ = 54 . 4 ◦ , and v = 58 m / s . At its highest point, the baseball has only a horizontal velocity v x = v cos θ contributing to its kinetic energy, so the kinetic energy is K = 1 2 mv 2 x = 1 2 m ( v cos θ ) 2 = 1 2 (1 . 26 kg)[(58 m / s) cos54 . 4 ◦ ] 2 = 718 . 167 J . keywords: 002 (part 1 of 2) 10 points A force ~ F = F x ˆ ı + F y ˆ acts on a particle that undergoes a displacement of ~s = s x ˆ ı + s y ˆ . Let: F x = 7 N, F y = 5 N, s x = 2 m, and s y = 2 m. Find the work done by the force on the particle. Correct answer: 4 J. Explanation: The work is given by W = ~ F · ~s = F x s x + F y s y = (7 N)(2 m) + ( 5 N)(2 m) = 4 J . 003 (part 2 of 2) 10 points Find the angle between ~ F and ~s . Correct answer: 80 . 5377 ◦ . Explanation: Since W = ~ F · ~s = fl fl fl ~ F fl fl fl  ~s  cos θ . The first and the third sides can be solved for θ to give θ = cos 1 W fl fl fl ~ F fl fl fl  ~s  ....
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 Spring '12
 James
 Physics, Force, Friction, Work, Correct Answer, θ, 98.9 N force

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