HW 8-solutions

HW 8-solutions - billing(cab4763 HW 8 opyrchal(11109 This...

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billing (cab4763) – HW 8 – opyrchal – (11109) 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points A(n) 51 . 6 kg astronaut becomes separated From the shuttle, while on a space walk. She fnds herselF 44 . 4 m away From the shuttle and moving with zero speed relative to the shuttle. She has a(n) 0 . 933 kg camera in her hand and decides to get back to the shuttle by throwing the camera at a speed oF 12 m / s in the direction away From the shuttle. How long will it take For her to reach the shuttle? Answer in minutes. Correct answer: 3 . 41051 min. Explanation: Let : M = 51 . 6 kg , m = 0 . 933 kg , d = 44 . 4 m , and v = 12 m / s . Because oF conservation oF linear momentum, we have 0 = M V + m ( - v ) mv = M V where V is the velocity oF the astronaut and it has a direction toward the shuttle. V = M = (0 . 933 kg) (12 m / s) 51 . 6 kg = 0 . 216977 m / s . And the time it takes For her to reach the shuttle t = d V = 44 . 4 m 0 . 216977 m / s · 1 min 60 s = 3 . 41051 min . 002 10.0 points A child bounces a 51 g superball on the side- walk. The velocity change oF the superball is From 22 m / s downward to 12 m / s upward. IF the contact time with the sidewalk is 1 800 s, what is the magnitude oF the average Force exerted on the superball by the sidewalk? Correct answer: 1387 . 2 N. Explanation: Let : m = 51 g = 0 . 051 kg , v u = 12 m / s , v d = 22 m / s , and Δ t = 0 . 00125 s Choose the upward direction as positive. The impulse is I = F Δ t = Δ P = u - m ( - v d ) = m ( v u + v d ) F = m ( v u + v d ) Δ t = (51 g) (12 m / s + 22 m / s) 0 . 00125 s = 1387 . 2 N . 003 (part 1 of 2) 10.0 points A(n) 17 g object moving to the right at 30 cm / s overtakes and collides elastically with a 31 g object moving in the same direction at 17 cm / s. ±ind the velocity oF the slower object aFter the collision. Correct answer: 13 . 2083 cm / s. Explanation: Basic Concepts: Momentum conserva- tion gives m 1 v 1 i + m 2 v 2 i = m 1 v 1 f + m 2 v 2 f . Solution: ±or head-on elastic collisions, we know that v 1 i - v 2 i = - ( v 1 f - v 2 f ) .
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billing (cab4763) – HW 8 – opyrchal – (11109) 2 For the relative velocities, we have v 1 - v 2 = v 2 f - v 1 f v 2 f = v 1 - v 2 + v 1 f . Momentum is conserved, so m 1 v 1 + m 2 v 2 = m 1 v 1 f + m 2 v 2 f m 1 v 1 + m 2 v 2 = m 1 v 1 f + m 2 ( v 1 - v 2 + v 1 f ) m 1 v 1 + m 2 v 2 - m 2 ( v 1 - v 2 ) = v 1 f ( m 1 + m 2 ) v 1 f = m 1 v 1 + m 2 v 2 - m 2 { v 1 - v 2 } m 1 + m 2 = 1 (17 g) + (31 g) × b (17 g)(30 cm / s) + (31 g)(17 cm / s) - (31 g) { (30 cm / s) - (17 cm / s) } B = 13 . 2083 cm / s .
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HW 8-solutions - billing(cab4763 HW 8 opyrchal(11109 This...

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