Newton’s Third Law of Motion

Newton’s Third Law of Motion

Newton's third law of motion was discovered and formulated, during the investigation of the fact that in all experiments it appeared that "whenever a body exerts a force on a second appeared that "whenever a body exerts a force on a second body, the second body always exerts a force on the first one".         Let us visualize and understand this phenomena with an experiment:         Suppose, we throw a stone on a surface of good strength; and the surface is made of glass, one finds it broken (the surface). From here one concludes that a force was exerted by stone on the surface and consequently it was broken.         Now, the question is, did that surface also exert a force on the stone. Just to know about it let us change our throwing object from stone to an egg of almost equal mass. Now, one throws this egg on the same surface of good strength with the same throwing force which he used for the stone. What happens? Obviously with your daily experience you know that the egg will be broken (And the damage to the surface will not be visible due to egg's spoiling the observation).         This is only possible if there was a force acting on the egg at the time it hit the surface. In fact we can now conclude that there is mutual force acting on the contact point of the surface and the object thrown. The breaking of either one (or may be both) depends on their ability to absorb forces without getting damaged (that is their strength) so in precise words:-         To every action there is always opposite and equal reaction, it is equivalent to say that mutual actions of two bodies upon each other are always equal and directed to contrary parts. Note: The most important fact to notice here is that these oppositely directed equal action and reaction can never balance or cancel each other because they always act, on two different point (broadly on two different objects) For balancing any two forces the first requirement is that they should act one one and the same object. (or point, if object can be treated as a point mass, which is a common practice).   Illustration of Newton's Third Law: Some of the examples of Newton's third law of motion are given below:  1.      Book kept on a table: A book lying on a table exerts a force on the table which is equal to the weight of the book. This is the force of action. The table supports the book, by exerting an equal force on the book. This is the force of reaction, as shown in the figure. As the system is at rest, net force on it is zero. Therefore, forces of action and reaction must be equal and opposite.