In the area of physics called Classical Mechanics, Newton’s three laws of motion are foundational concepts. Newton, in 1686, presented his three laws of motion in the book Principia Mathematica Philosophiae Naturalis. The third law of motion states that
” When one body exerts some amount of force on another body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.”
This is often translated to every action has an equal and opposite reaction. Newtons third law is probably the most famous of the three because people generally relate it to non-physics situations.
Newton’s third law is crucial because it implies that every force has a side effect which is felt like the opposite force by exerted by the second body. This is seen in collisions. Take elastic collisions where no amount of energy is absorbed or dissipated. Here, imagine a scenario where one golf ball hits another with some force F, this means that at the time they both hit, the second golf ball also applies the same amount of force F in the opposite direction on the first ball. Hence, the first ball bounces of the second, and both of them then move in opposite directions.
This might seem like a simple idea at first, but if we think of a bigger picture, this is how our rockets work. The huge body of the rocket is only bolstered by the highly accelerated gas that comes out of it from the bottom. The chemicals from the bottom have a very small mass, but due to the amount of acceleration they have, they produce enough force to propel a rocket into space! This wouldn’t be possible if Newton did not publish the third law of motion in 1686. It is fascinating how such a simple principle of nature has lead us to create so many things. We have created great technologies with even the simplest of clues about the workings of the universe.
Newton’s third law remains one of the most used laws in classical physics. Although now we know that classical physics is not perfect, it is one of the best approximations to reality we can find. The third law is also seen in guns. When a shooter fires a gun because the bullet moves with high acceleration, it produces an opposite force on the gun, and thus the shooter will feel a jerk after the bullet is fired.
Newton’s third law can also be seen in action in ice skating. On the ice, friction is almost zero, and hence a moving object will continue to move as is stated by Newton’s first law. But, for an ice skater to move, he must somehow apply a force on himself. So, an ice skater can only move by pushing an object or another person in the opposite direction to where he wants to go. So, Newton’s laws of motion are present everywhere, and we can observe them even in daily life. They are still being used in physics extensively and have provided the foundation for the wonderful technology we now use every day.