Newtons Laws of Motion I- The 3 Laws


Many of you are already familiar with the three laws of motion that Sir Issac Newton proposed in the late 1600’s. Newton’s Laws are the pillars of classical mechanics. The formation of these Laws paved way for the Industrial Revolution which played a big role in shaping modern society.

In NLM, we will study about atwood machines, pulleys, levers and many other objects. We will investigate all the machines one by one. But before that, we shall learn the three laws.

Newton’s First law of motion

law that Sir Issacs Newton proposed is the law of inertia. Inertia is also called ‘Resistance to change’. The first law states that a body continues to be in state of rest or uniform motion in straight line until it is expelled by an external force. What this means is that if you see a body lying on the ground/platform then, its on it and cannot start in motion. But, if you try to push it with your fingers then the body starts moving. Hence you applied a force to overcome the resistance that the body had. When the body is forced in motion then the body gains kinetic energy. (We will learn about this in work, energy and power). As everything in the universe wants to be at its lowest energy state, things stay at rest. Only external force can alter the state of the body.

Newton’s second law of motion

Newton;s Second law is the most important Law. In fact, the First and Third Law are unnecessary. They can be deduced from the Second Law itself. The second Law was the spark for the industrial revolution.

The above photo shows the Industrial Revolution

The second law states that the acceleration of an object is directly proportional to the force applied and inversely proportional to the mass of the object. Mathematically, the second law is given as follows:

a= F(net) / m

The Second law will be discussed in much more detail in a following article.

Newton’s Third Law of Motion

Newton’s third law is the most commonly known law. it states that every action has an equal and opposite reaction. A simple way to think about this is to imagine two objects A and B. If A applies a force on B in the positive direction, then B will apply an equal force on A in the negative direction.

Rockets also work on this concept. They eject a huge amount of mass from one end at a huge speed towards the ground. The ejected mass applies an equal force in the upward direction, therefore, propelling the rocket upwards.

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