Two spaceships are observed from Earth to be approaching each other along a straight line. Ship A moves at \(0.40 c\) relative to the Earth observer, and ship \(\mathrm{B}\) moves at \(0.50 c\) relative to the same observer. What speed does the captain of ship A report for the speed of ship B?

Short Answer

Expert verified
Answer: The speed of ship B as observed by the captain of ship A is 0.125c.

Step by step solution

01

List the given information and the unknown

The given information is as follows: - Velocity of ship A relative to Earth, \(v_A = 0.40 c\) - Velocity of ship B relative to Earth, \(v_B = 0.50 c\) - We need to find the velocity of ship B relative to ship A, denoted as \(v_{BA}\)
02

Use the formula for relative velocity in special relativity

In special relativity, the formula for calculating the relative velocity is given by the following equation: $$v_{BA} = \frac{v_B - v_A}{1 - \frac{v_A v_B}{c^2}}$$
03

Solve for the unknown and give the final answer

Now, substituting the given values of \(v_A\) and \(v_B\) into the formula, we get: $$v_{BA}= \frac{0.50 c - 0.40 c}{1 - \frac{0.40 c \times 0.50 c}{c^2}}$$ Simplifying, we have: $$v_{BA}=\frac{0.10 c}{1 - 0.20} = \frac{0.10 c}{0.80}$$ Finally, we find the relative velocity of ship B as observed by the captain of ship A: $$v_{BA} = \frac{0.10}{0.80} c = 0.125 c$$ Therefore, the captain of ship A reports the speed of ship B to be \(0.125c\).

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