If you see Al going to your left at exactly 0.99c and Bob going to your right at exactly 0.99c,Al will say that Bob is
A)going away from her at 1.98c.
B)going away from her at exactly 0.99c.
C)going away from her at exactly c.
D)going away from her at about 0.98c.
E)going away from her faster than 0.99c,but slower than c.

Question

Quizplus · Accepted Answer

According to the theory of relativity, velocities don't simply add together. When Al observes Bob's velocity, it must be calculated using the relativistic velocity addition formula: $v = \frac{v_1 + v_2}{1 + \frac{v_1v_2}{c^2}}$, where $v_1$ and $v_2$ are the velocities of Al and Bob respectively, and $c$ is the speed of light. Plugging in $v_1 = 0.99c$ and $v_2 = 0.99c$, the result is a velocity less than $c$, but greater than $0.99c$, which matches choice E.

If You See Al Going to Your Left at Exactly