WHEN AN OBJECT RESISTS A FORCE THAT IS APPLIED TO IT, IT APPLIES A FORCE BACK THAT IS EQUAL IN SIZE BUT OPPOSITE IN DIRECTION.

All objects resist a change in their motion. Based on their mass, they resist when forces are applied. This inertia causes an equal magnitude and opposite direction force to be applied back on the first object. When objects do not have a large resistance to applied forces, it is difficult to apply large forces to them. For example, when you push a real car, you may be able to apply hundreds of Newtons of force to it to get it to roll, but a toy car would move quickly away from you before you applied anywhere near one hundred Newtons of force to it. When you feel an object resist the force you are applying to it, you are feeling this reaction force.