A spaceship traveling at constant speed passes by Earth and later ...

[Lobcity]

A spaceship traveling at constant speed passes by Earth and later passes by Mars. In which frame of reference is the amount of time separating these two events the proper time?
 
  A) the Earth frame of reference
  B) the Mars frame of reference
  C) the spaceship frame of reference
  D) any inertial frame of reference
  E) any frame of reference, inertial or not

Question 2

A heat engine absorbs 64 kcal of heat each cycle and exhausts 42 kcal. (a) Calculate the efficiency each cycle. (b) Calculate the work done each cycle.
 
  What will be an ideal response?

[frogdreck123456]

Answer to Question 1

C

Answer to Question 2

(a) 34
(b) 22 kcal

[Lobcity]

Wow, this really help

[kilada]

Thanks for the timely response, appreciate it