need help with relativity question

[Samueliscool223]

For question 8e (see image attached below), im a bit confused since the books answers says youre supposed to do t = d/v = 4/50, yet i did d/v = 5/(50+10), as i thought you were supposed to add the speed of light and the velocity of the moving train (in Chloe's frame of reference) to get 60 for v, and that youd get 5 for d as theyre 5m apart. so can someone explain to me why the answer is 4/50, thanks

[eman27_hc]

For question 8e (see image attached below), im a bit confused since the books answers says youre supposed to do t = d/v = 4/50, yet i did d/v = 5/(50+10), as i thought you were supposed to add the speed of light and the velocity of the moving train (in Chloe's frame of reference) to get 60 for v, and that youd get 5 for d as theyre 5m apart. so can someone explain to me why the answer is 4/50, thanks

With Special relativity, the speed of light is not an additive process. So the line, " i thought you were supposed to add the speed of light" is wrong. Remember, Einstein's second postulate states "the speed of light c is a constant, independent of the relative motion of the source". Therefore, the speed of light will be 50 m/s for both Chloe, Anna, and Ben - regardless of their frame of reference.

Hopes this help