Which term means a pulling force exerted on a limb in a distal direction in an effort to return the bone or joint to normal alignment?

Which one of the following research methods can show cause and effect

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •  

The law of the conservation of momentum says that the total momentum of any closed and isolated system cannot