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Homework #9 - Linear momentum-solutions

# Homework #9 - Linear momentum-solutions - sanchez(es25396...

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sanchez (es25396) – Homework #9 - Linear momentum – guevara – (130101) 1 This print-out should have 13 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 points In a particular crash test, an automobile of mass 1431 kg collides with a wall and bounces back off the wall. The x components of the initial and final speeds of the automobile are 16 m / s and 1 . 7 m / s, respectively. If the collision lasts for 0 . 14 s, find the magnitude of the impulse due to the collision. Correct answer: 25328 . 7 kg · m / s. Explanation: Let : m = 1431 kg , v i = 16 m / s , v f = 1 . 7 m / s , and Δ t = 0 . 14 s . The initial and final momenta of the auto- mobile are vectorp i = mvectorv i = (1431 kg) ( 16 m / s) = ( 22896 kg · m / s)ˆ ı vectorp f = mvectorv f = (1431 kg) (1 . 7 m / s) = (2432 . 7 kg · m / s)ˆ ı . Thus the impulse is vector I = Δ vectorp = vectorp f vectorp i = [(2432 . 7 kg · m / s) ( 22896 kg · m / s)] ˆ ı = (25328 . 7 kg · m / s)ˆ ı , with magnitude 25328 . 7 kg · m / s . 002 (part 2 of 2) 10.0 points Calculate the magnitude of the average force exerted on the automobile during the colli- sion. Correct answer: 1 . 80919 × 10 5 N. Explanation: The average force exerted on the automo- bile during the collision is ¯ F = Δ vectorp Δ t = (25328 . 7 kg · m / s) (0 . 14 s) ˆ ı = (1 . 80919 × 10 5 N) ˆ ı with magnitude 1 . 80919 × 10 5 N . 003 (part 1 of 2) 10.0 points A force of 7 . 85 N acts on a(n) 2 . 1 kg object for 16 . 3 s. What is the object’s change in momentum? Correct answer: 127 . 955 N · s. Explanation: Let : F = 7 . 85 N and Δ t = 16 . 3 s . Δ p = F Δ t = (7 . 85 N) (16 . 3 s) = 127 . 955 N · s . 004 (part 2 of 2) 10.0 points What is its change in velocity? Correct answer: 60 . 931 m / s. Explanation: Let : m = 2 . 1 kg . Δ p = m Δ v Δ v = Δ p m = 127 . 955 N · s 2 . 1 kg = 60 . 931 m / s .

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Homework #9 - Linear momentum-solutions - sanchez(es25396...

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