Laws of motion


Introduction

In this blog, we will study about the case of the motion due to the force. Force is the central problem in the mechanics. From day to day life experience we define the force as push or pull. One of the effects of the force is to produce motion to a rest body or to bring at rest to a moving body.
If all the particles of the object move in the same way, the motion is translational and the object is considered as point object. If the particle of the object has different linear displacement but same angular displacement, rotational motion takes place. For example, a rolling ball. In this chapter we discuss about the basic laws of motion due to the force. Newton studied about motion scientifically and
concluded some results which are called Newton's laws of motion. There are three laws of motion. All three laws define force in different ways. First law defines force qualitatively, second law defines quantitatively and third law highlights that single and isolated force is not possible.
A force can cause both the translation as well as rotational motion on an object.

Newton's Laws of Motion

Newton's First Law of Motion

According to this law, everybody in this universe continues in its state of rest or of uniform motion in a straight line unless it is compelled by some external force to change the state.
From the above statement we conclude that to change the state of rest or motion, an external agent is required which is called the force. Internal force does not produce motion in total. The 1st law gives the definition of force.
Newton’s second law of motion
Newton’s second law of motion states that the rate of change of momentum is directly proportional to the net external force applied on it and the change takes place in the direction of force.
When a force F is applied on a body whose momentum at time is p, then from Newton’s second law
F=ma.
This equation gives the magnitude of force.

Newton’s third law of motion

It states that, to every action there is always an equal and opposite reaction.
          According to above statement, forces occur in a pair only because of action and reaction. Since the force act on the different body, action and reaction do not cancel to each other.


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