PHYS171_f11_exam_4_solution

# PHYS171_f11_exam_4_solution - PHYS171 Name: _ Exam 4 Fall...

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PHYS171 Exam 4 Fall 2011 Name: _____________________ Student ID #: ________ 1 Questions 1) Explain in a few sentences (and possibly a diagram) why it is not possible to say with certainty that two events which occur at different locations are simultaneous. Be sure to make clear how the postulates of the theory of special relativity are involved. (10 points) It events occur at the same location we can determine if they are simultaneous without ambiguity. If they are at different locations, we must record the events using clocks at the two locations and compare the readings. However it will be impossible to say for sure that the clocks are synchronized if they are at different locations. If an observer at rest with respect to the clocks judges them synchronized, an observer moving with respect to the clocks will judge them not synchronized. This can be seen from the Lorenz transformation of time. Another way to describe this is to consider an observer midway between the clocks. Suppose an observer at rest with respect to the clocks sees ‘ticks’ from the clocks arriving at the same time and judges them synchronized. An observer moving with respect to the clocks will see the clock she is moving towards tick first. In classical mechanics we would explain this by saying the waves appear to be coming faster when you approach the source, but in special relativity the speed of light is the same in all reference frames, and there is no way of decided which observer is correct about the synchronization of the clocks. 2)

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## This note was uploaded on 12/29/2011 for the course PHYSICS 171 taught by Professor La porta during the Fall '11 term at Maryland.

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PHYS171_f11_exam_4_solution - PHYS171 Name: _ Exam 4 Fall...

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