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Unformatted text preview: 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 (part 1 of 3) 10.0 points 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. . 1 c Earth Determine its length as measured by a per- son on Earth. Correct answer: 39 . 7995 m. Explanation: Let : L = 40 m and v = 0 . 1 c. Applying length contraction, L = L = L radicalBigg 1- v 2 c 2 = (40 m) radicalbigg 1- (0 . 1 c ) 2 c 2 = 39 . 7995 m . 002 (part 2 of 3) 10.0 points 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: T = T = 2 years . 994987 = 2 . 01008 years . 003 (part 3 of 3) 10.0 points 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 10.0 points 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 10.0 points A passenger on an interplanetary express bus traveling at v = 0 . 95 c takes a 3 minute cat- nap by his watch. 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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This note was uploaded on 11/10/2011 for the course PHYSICS 303L taught by Professor Hoffman during the Fall '11 term at University of Texas at Austin.
- Fall '11