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kostasdb
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Homework Statement
A 20 m long stick is flying with 90% of the speed of light along the x-axis relative to S. From our vantage point (S), it flies behind and parallel to a building that is 10 m long in the x-direction. Which of the following statements is not true?
1 The stick appears to have a length of only 8.72 m in S.
2 At some point in time, the stick is observed (according to careful measurements in S) to be behind the building in its entire length.
3 The stick does not have a "true" (rest)length, it is completely arbitrary which coordinate system one uses to measure its length, and every coordinate system will give a different but equally valid answer.
4 From the point of view of S', the building is way too short to obscure the stick at any time.
The Attempt at a Solution
All 4 statements seem true to me The stick does seem to be 8.72 m long according to S (L=L’/y=20m/2.294=8.72m). The building according to S’ would be 4.4m according to it(using the same formula as before) and too small to conceal the stick. All frames of reference are equally valid and technically, from S frame of reference the 8.72m stick can be behind a 10 m building. I must be missing something small here...