Newton's Third Law:


You cannot touch without being touched. Any time two objects come into contact, THEY BOTH COME INTO CONTACT. Any push exerted by one must therefore be felt by the other as well. We can visualize this by imagining a person pushing a heavy dresser or desk across the floor. At first it seems that all of the push is exerted by the person onto the object, but it the same situation occurred on a frozen lake or if the person were standing on a skateboard, it would be easy to see by the person's acceleration that the dresser or desk is exerting force on them as well.

One result of adding Newton's Second Law to Newton's Third Law is that we will see that for the same amount of force, two different objects in contact can experience very different accelerations.

m a is equal to F which is also equal to ma
small mass, big acceleration = big mass, small acceleration when the same force is applied to each.