A spaceship is moving in a straight line away from Earth at 0.80c,measured relative to Earth.It launches a missile that moves away from the spaceship in the forward direction at 0.60c,relative to the ship.Relative to Earth,what is the speed of this missile?
A)greater than 0.80c but less than c
B)1.4 c
C)c
D)greater than c but less than 1.4c

Question

Quizplus · Accepted Answer

According to the theory of relativity, velocities don't simply add together. The relative speed of the missile with respect to Earth is given by the formula for relativistic velocity addition: $v = \frac{v_1 + v_2}{1 + \frac{v_1 \cdot v_2}{c^2}}$, where $v_1 = 0.80c$ is the speed of the spaceship relative to Earth, $v_2 = 0.60c$ is the speed of the missile relative to the spaceship, and $c$ is the speed of light. Substituting these values, we find that the speed of the missile relative to Earth is greater than $0.80c$ but less than $c$, ensuring that the speed of any object relative to another cannot exceed the speed of light.

A Spaceship Is Moving in a Straight Line Away from Earth