# 40_new - Ch1-H2 florin(56950 This print-out should have 30...

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Ch1-H2 – florin – (56950) 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 7) 3.0 points A spacecraft is observed to be at loca-tion h200 m, 300 m, −400 mO relative to an origin located on a nearby asteroid, and 5 s later it is observed to be at location h475 m, 100 m, −650 mO . Find the average velocity of the spacecraft, v¯ = hv x , v y , v z O . What is v x in m/s? Correct answer: 55 m/s. Explanation: The average velocity of the spacecraft is calculated by finding the change of position over a change in time: v¯ = ~r f ~r i . t Because ~r is a vector, the average velocity will also be a vector and each component must be calculated separately. For v¯ x the value becomes: x = v 2 x v 1 x t = (475 m) − (200 m) (5 s) = 55 m/s 3 (part 2 of 7) 3.0 points What is v y in m/s? Correct answer: −40 m/s. Explanation: The average velocity of the spacecraft is calculated by finding the change of position over a change in time: v¯ = ~r f ~r i . t Because ~r is a vector, the average velocity will also be a vector and each component must be calculated separately. For v¯ y the value becomes: y = v 2 y v 1 y t = (100 m) − (300 m) (5 s) = −40 m/s 4 (part 3 of 7) 3.0 points What is v z in m/s? Correct answer: −50 m/s. Explanation: The average velocity of the spacecraft is calculated by finding the change of position over a change in time: v¯ = ~r f ~r i . t Because ~r is a vector, the average velocity will also be a vector and each component must be calculated separately. For v¯ z the value becomes: z = v 2 z v 1 z t = (−650 m) − (−400 m) (5 s) = −50 m/s 5 (part 4 of 7) 2.0 points What is |~v| in m/s? Correct answer: 84.4097 m/s. Explanation: The magnitude is calculated by: q |~v| = v x 2 + v y 2 + v z 2 q = (55 m/s) 2 + (−40 m/s) 2 + (−50 m/s) 2 = 84.4097 m/s 5 (part 5 of 7) 3.0 points

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Ch1-H2 – florin – (56950) 2 Find the unit vector in the direction of the For example: velocity of the spacecraft, vˆ = hvˆ x , vˆ y , vˆ z O . z = v z What is vˆ x ? |~v| = −50 m/s Correct answer: 0.651584. 84.4097 m/s Explanation: = −0.592349 The unit vector for a vector is given as : hv x , v y , v z O 008 (part 1 of 7) 3.0 points vˆ = hvˆ x , vˆ y , vˆ z O = Here are the positions at three di f erent |~v| times for a bee in flight (a bee’s top speed is For example: about 7m/s . x = v x T ime P osition |~v| 9.5 s h−2.5 m, 10.4 m, 0 mO 55 m/s 10 s h−0.3 m, 7.2 m, 0 mO = 84 .4097 m/s 10.5 s h1.5 m, 2.7 m, 0 mO = 0.651584 Between 9.5 s and 10 s, find the bee’s aver- 006 (part 6 of 7) 3.0 points age velocity: A A A What is vˆ y ? = hv x , v y , 0O . Correct answer:
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40_new - Ch1-H2 florin(56950 This print-out should have 30...

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