If you consider a bullet firing from a gun then you have conservation of momentum and a Newton's third law pair (according to what i have read on the internet anyway). They both experience the same force if they are a third law pair but, generally, what is it that determines which object receives more energy? For instance, the bullet has a huge kinetic energy after the gun has fired whereas the gun has very little. So where does energy conservation fit into this example and what is the relationship between energy and force (if there is one)? They are both receiving the same force yet experience different energies?