Observer A sees a ruler moving by in a relativistic train and ...

[dbose]

Observer A sees a ruler moving by in a relativistic train and measures its length to be LA. Observer B moves together with the train and measures the length of the ruler to be LB. These two results will be such that
 
  A) LA > LB.
  B) LA = LB.
  C) LA < LB.
  D) LA could be greater or smaller than LB depending on the direction of the motion.

Question 2

A refrigerator has a COP of 2.5. If it removes 7.7 MJ of heat in 25. minutes,
 
  (a) what is the minimum power motor to operate the refrigerator?
  (b) what is its efficiency if it were a reversible engine?

[milbourne11]

Answer to Question 1

C

Answer to Question 2

(a) 2.1 kW
(b) 29. efficiency

[dbose]

Great answer, keep it coming

[Dominic]

Thanks for the timely response, appreciate it