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# HW 9 - segovia(cs39966 Homework 9 Spurlock(14441 This...

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segovia (cs39966) – Homework 9 – Spurlock – (14441) 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001(part1of3)10.0points A spaceship travels with a speed of 0 . 1 c as it passes by the Earth on its way to a distant star, as shown in the diagram below. The pilot of the spaceship measures the length of the moving ship as 40 m. 0 . 1 c Earth Determine its length as measured by a per- son on Earth. Correct answer: 39 . 7995 m. Explanation: Let : L 0 = 40 m and v = 0 . 1 c . Applying length contraction, L = L 0 γ = L 0 radicalBigg 1 - v 2 c 2 = (40 m) radicalbigg 1 - (0 . 1 c ) 2 c 2 = 39 . 7995 m . 002(part2of3)10.0points The pilot of the spaceship observes that the spaceship travels for 2 years. Determine how much time has passed ac- cording to a person on Earth. Correct answer: 2 . 01008 years. Explanation: Δ T = Δ T 0 γ = 2 years 0 . 994987 = 2 . 01008 years . 003(part3of3)10.0points Some time after passing the Earth, the pilot shoots a laser pulse backward at a speed of 3 × 10 8 m / s with respect to the spaceship. Determine the speed of the laser pulse as measured by a person on Earth. Correct answer: 3 × 10 8 m / s. Explanation: A laser pulse travels at the speed of light, in- dependent of the frame in which it is measured ( the key point of special relativity). Thus the Earth observer sees the pulse traveling at the same speed as the pilot, 3 × 10 8 m / s . 004 10.0points A spaceship is measured to be 183 m long while at rest relative to the observer. If this spaceship now flies by the observer with a speed 0 . 967 times the speed of light, what length does the observer measure? Correct answer: 46 . 6241 m. Explanation: Let : L p = 183 m and v = 0 . 967 c . If L p is the proper length of the moving object, the length of the spacecraft measured by the observer is L = L p radicalbigg 1 - v 2 c 2 = (183 m) radicalBig 1 - (0 . 967) 2 = 46 . 6241 m . 005 10.0points A passenger on an interplanetary express bus traveling at v = 0 . 95 c takes a 3 minute cat- nap by his watch.

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segovia (cs39966) – Homework 9 – Spurlock – (14441) 2 How long does the nap last from your van- tage point on a fixed planet?
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HW 9 - segovia(cs39966 Homework 9 Spurlock(14441 This...

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