I have a quick question on Newton's third law.
When a 100kg astronaut in space is holding a 100 kg rock and then pushes it away from him with 50 joules of energy (the kinetic energy put into the system) and a second astronaut (observer) is watching, sitting still relatively to the location where the other astronaut was holding the rock and generating the 50 joules before the push, does the observer see the rock float to the left of him with 1 m/s and the astronaut float to the right of him with 1 m/s or does he see the rock float to the left with 0.707 m/s and the astronaut to the right with 0.707 m/s? In other words, is the total kinetic energy he observes equal to 100 joules or 50 joules?
When a 100kg astronaut in space is holding a 100 kg rock and then pushes it away from him with 50 joules of energy (the kinetic energy put into the system) and a second astronaut (observer) is watching, sitting still relatively to the location where the other astronaut was holding the rock and generating the 50 joules before the push, does the observer see the rock float to the left of him with 1 m/s and the astronaut float to the right of him with 1 m/s or does he see the rock float to the left with 0.707 m/s and the astronaut to the right with 0.707 m/s? In other words, is the total kinetic energy he observes equal to 100 joules or 50 joules?