As measured from the Earth,a spacecraft is moving at speed 0.80c toward a second spacecraft moving at speed 0.60c back toward the first spacecraft.What is the speed of the first spacecraft as viewed from the second spacecraft?
A)0.81c
B)0.95c
C)0.38c
D)0.20c

Question

Quizplus · Accepted Answer

The speed of the first spacecraft as viewed from the second spacecraft can be calculated using the formula for relativistic velocity addition: $v = \frac{v_1 + v_2}{1 + \frac{v_1 \cdot v_2}{c^2}}$, where $v_1 = 0.80c$ and $v_2 = -0.60c$ (negative because it's moving in the opposite direction). Plugging these values in gives a result of approximately $0.95c$, which corresponds to choice B.

As Measured from the Earth,a Spacecraft Is Moving at Speed