Question

Two rockets of rest length L approach each other with equal speeds of 0.4c. How

long would one rocket appear to the other?
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Answer 1

Answer:

Explanation: In this case v = 0.4c and uₓ = -0.4c

So the relative  speed of the rocket is from the formula

U'ₓ = uₓ - v / 1- vuₓ/c²

U'ₓ = -0.4c - 0.4c / 1- (0.4c -0.4c) /c²

 U'ₓ = - 1.6c / 1 + 0.61

U'ₓ = 1.6c / 1.61

U'ₓ= 0.9937c