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Unformatted text preview: khounvivongsy (sk27799) – Homework 12 – 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 A 3 kg steel ball strikes a wall with a speed of 15 . 6 m / s at an angle of 36 ◦ with the normal to the wall. It bounces off with the same speed and angle, as shown in the figure. x y 1 5 . 6 m / s 3 kg 1 5 . 6 m / s 3 kg 36 ◦ 36 ◦ If the ball is in contact with the wall for . 106 s, what is the magnitude of the average force exerted on the ball by the wall? Correct answer: 714 . 377 N. Explanation: Let : M = 3 kg , v = 15 . 6 m / s , and θ = 36 ◦ . The y component of the momentum is un changed. The x component of the momentum is changed by Δ P x = − 2 M v cos θ . Therefore, using impulse formula, F = Δ P Δ t = − 2 M v cos θ Δ t = − 2 (3 kg) (15 . 6 m / s) cos 36 ◦ . 106 s bardbl vector F bardbl = 714 . 377 N . Note: The direction of the force is in negative x direction, as indicated by the minus sign. 002 10.0 points A golf ball ( m = 62 . 6 g) is struck a blow that makes an angle of 60 . 9 ◦ with the horizontal. The drive lands 103 m away on a flat fairway. The acceleration of gravity is 9 . 8 m / s 2 . If the golf club and ball are in contact for 9 . 9 ms, what is the average force of impact? Neglect air resistance. Correct answer: 217 . 916 N. Explanation: Let : g = 9 . 8 m / s 2 , m = 62 . 6 g , θ = 60 . 9 ◦ , and t = 9 . 9 ms . Note that the range of the golf ball is given by L = v 2 sin2 θ g , so the initial velocity of the ball is v = radicalBigg L g sin(2 θ ) = radicalBigg (103 m) (9 . 8 m / s 2 ) sin(2 × 60 . 9 ◦ ) = 34 . 4627 m / s . The average force exerted is the change in its momentum over the time of contact F = mv t = (62 . 6 g) (0 . 001 kg / g) (34 . 4627 m / s) (9 . 9 ms) (0 . 001 s / ms) = 217 . 916 N . 003 10.0 points A 3 . 59 kg particle has a velocity of v x = 3 . 64 m / s and v y = 4 . 56 m / s....
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This note was uploaded on 02/08/2010 for the course PHYS 1710 taught by Professor Weathers during the Spring '09 term at University of North Carolina Wilmington.
 Spring '09
 weathers
 Physics

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