Third Law of Motion

 Newton’s third law states that any force exerted by one object to a second object is met by an equal magnitude and opposite direction force from the second object to the first object. You can imagine that, if you push your friend while you and your friend are standing on a frictionless surface, both you and your friend will move away from each other in opposite directions! Rocket launches work on this principle: the rocket burns fuel to push at the earth, which in turn accelerates the rocket in the opposite direction. The earth does not accelerate very much at all, since it is much more massive than the rocket.  

An important concept to note is that it is the magnitude of the force that is equal, not the resulting accelerations of the force. Remember Newton’s second law of motion:  

F = m a 

Every force is met with an equal and opposite force, but the resulting accelerations scale inversely with the mass of the object accelerating. This is why, when a rocket launches, the rocket accelerates quite a bit, but the earth does not. It takes more force to accelerate a very massive object than it does to accelerate a less massive object.