Observer A sees a ruler moving by in a relativistic rocket and measures its length to be LA. Observer B moves along with the rocket and measures the length of the ruler to be LB. What is true About these two length measurements? A) $L A L _ { B }$ C) $L _ { A } = L _ { B }$ D) $L _ { A }$ could be greater or smaller than $L _ { B }$ depending on the direction of the motion.

Question

Observer A sees a ruler moving by in a relativistic rocket and measures its length to be LA. Observer B moves along with the rocket and measures the length of the ruler to be LB. What is true
About these two length measurements? 
A) $L A < L _ { B }$
B) $L _ { A } > L _ { B }$
C) $L _ { A } = L _ { B }$
D) $L _ { A }$ could be greater or smaller than $L _ { B }$ depending on the direction of the motion.

Quizplus · Accepted Answer

According to the theory of relativity, an object in motion appears shorter to a stationary observer compared to an observer moving with the object. Therefore, $L_A < L_B$, as observer A sees the ruler moving and measures it to be shorter than observer B, who moves along with the ruler.

Observer a Sees a Ruler Moving by in a Relativistic LA<LBL A < L _ { B }LA<LB​

Observer a Sees a Ruler Moving by in a Relativistic $L A < L _ { B }$