Question

Galaxy B moves away from galaxy A at 0.511 times the speed of light. Galaxy C moves away from galaxy B in the same direction at 0.743 times the speed of light. How fast does galaxy C recede from galaxy A. Express your answer as a fraction of the speed of light.

Answer 1

0.90891c

Step-by-step explanation:

u = Speed of Galaxy B relative to Galaxy A = 0.511c

v = Speed of Galaxy C relative to Galaxy B = 0.743c

c = Speed of light

Relativistic equation for velocity is given by

`w=(u+v)/(1+(uv)/(c^2))\\\Rightarrow w=(0.511+0.743)/(1+(0.511c* 0.743c)/(c^2))\\\Rightarrow w=0.90891c`

The speed at which galaxy C recedes from galaxy A is 0.90891c