I know this is rather basic, but some how I confused myself... The question is: An astronaut of mass 75 kg performs repair work on the 1700 kg satellite, while floating right next to it. He exerts a force of 180 N on the satellite. What is his acceleration as a consequence of this, and what is the acceleration of the satellite? Ok, I know the force acting on the satellite is 180 N and the force acting on the astronaut is -180 N, because newtons 3rd law (F=-F) Now here is my main question. I know to solve I need to Use F=MA for both the astronaut and satellite but, is their mass relevant? So is it: Astronaut: F/M =A -180/75 =A OR -180/75=A -2.4 m/(s^2) und =A Satellite: 180/1700 =A or 180/0= A .105882 m/s^2 =A und=A Sorry, for asking such a duh! kind of question but, I am taking AP Physics as an online course and the grading policy is crazy and the teacher and course mat'ls are useless.