- Homework Statement
- Ive noticed that in doing a lot of physics questions, identifying the location of the reaction force can be very difficult.
- Relevant Equations
- F1,2 = -F2,1
eg. For a ball in free fall (ignoring air resistance) there is only one force acting if the system is just considered to be the ball. It seems necessary to go to the system which includes the Earth for identification of the reaction force to be made. Is there any rule for how big a system must be in order for Newtons Third Law to be obeyed within that system (ie both the action and reaction forces to be identified within it)?