Exam-style question
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A spaceship moves at 0.8c relative to Earth. Describe how its length along the direction of motion would be observed from Earth, and write the equation that gives the observed length in terms of its proper length.
Model answer
What a good answer should say
- The length observed from Earth is shorter than the proper length.
- It is given by L = L0 sqrt(1 - v^2/c^2).
- For v = 0.8c, the factor sqrt(1 - 0.64) = sqrt(0.36) = 0.6, so the observed length is 0.6 L0.
Explanation
Why this works
This answer demonstrates understanding of length contraction, correctly states the equation, and applies it to a specific velocity, showing the ability to use the formula conceptually.
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