So far, we have come across first and second law of motion. In first law of motion, we learnt that every object tends to remain in its state of motion, until an external force is compelled to change the state. In second low of motion, we described that the rate of change of momentum of an object is proportional to the applied unbalanced force in the direction of force. From first and second law of motion, we know that if an object is in state of rest it will stay in that state until an external force is applied. When an external force is applied, now this object has a momentum. What if the object A1 with momentum P1 collides with an object A2 possessing momentum P2? How momentum will change, distribute, or will be lost after collision?
In this situation, let’s suppose the Collison is a head on collision. From the collision theory, which will be discussed in our upcoming blogs, we know that in a head on collision, no amount of velocity is lost. When velocity is conserved, and mass of the object is constant the momentum will remain conserve. In other word, sum of momentum of both objects will remain constant before and after collision. This property of momentum is known as conservation of momentum.
Newton explained this property under his third law of motion as action and reaction. He said that, if an object is doing some action on other object, other object will also do same amount of reaction in return. This reaction will be exactly equal to the amount of action but in opposite direction. For example, if an object A1 possessing momentum P1 collides with other object A2 possessing momentum P2. Then distribution of momentum will occur. In this case, object A1 did some action on Object A2 transferring some momentum and object A2 did reaction transferring some momentum back.
In this case both action and reaction occurred as Newton’s third law of motion stated, “to every action there is an equal and opposite reaction”. This phenomenon of action and reaction has been observed in many aspects of daily life like firing a gun, jumping off the boat, walking on the ground, kicking a football, and hitting a ball etc.
All the laws of Newton’s were the marvelous laws in the history of classical physics. These laws were the revolution in the study of physics. There are too much to explore about these laws. But here we put a full stop on this is topic for now. In next blog, we will discuss about gravitational force.
