NEWTONS LAW’S OF MOTION BY DR AJAY KUMAR

INTRODUCTION Sir Issac Newton in the seventeenth century formulated three laws of motion which explain why objects move. Although all of the three laws cannot be proved on earth even in ideal experimental situations, but they are accepted as universal truth to explain the effect of force.

NEWTON’S FIRST LAW (LAW OF INERTIA) Newton’s first law of motion states that a body continues in its state of rest or uniform motion unless an unbalanced or external force acts on it. or Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

UNDERSTANDING OF NEWTON’S FIRST LAW OF MOTION The fact that the objects at rest will remain rest can be understood but, The fact that a body in motion will remain in motion is not always as apparent. It needs some understanding. The tendency for a body to maintain it state of motion can be more understood in a lab condition.

UNDERSTANDING OF NEWTON’S FIRST LAW OF MOTION In lab when the effect of air resistance and friction is removed this concept can be understood more easily. We all sometime or other experience the effect of Newton’s first law of motion.

UNDERSTANDING OF NEWTON’S FIRST LAW OF MOTION The property of an object which causes it to remain in its state of either rest or in uniform motion is called its inertia. The amount of force needed to alter the objects inertia in a body is directly to the amount of inertia it posses.

UNDERSTANDING OF NEWTON’S FIRST LAW OF MOTION The measure of the inertia in a body is its mass i.e. the quantity of matter it possesses. The greater the mass of an object, the greater its inertia.

NEWTON’S SECOND LAW (LAW OF ACCLERATION) The second law of motion concerns acceleration and momentum, and tells how the quantity of force, mass and acceleration are related.

LAW OF ACCLERATION The acceleration of an object is directly proportional to the force causing it, is in the same direction as the force, and is inversely proportional to the mass of the object. or The rate of change of momentum of a body is proportional to the resultant force acting on the body and is in the same direction.

UNDERSTANDING OF NEWTON’S SECOND LAW OF MOTION It is quite easy to show that change in velocity (acceleration )of an object is proportional to the force and in the direction of force. Similarly it takes less stopping force to stop an object moving with less velocity (acceleration)

UNDERSTANDING OF NEWTON’S SECOND LAW OF MOTION As the mass of the objects is the measure of the inertia of the object it is clearly obvious that more mass require more force to produce motion or to stop motion and vice versa.

UNDERSTANDING OF NEWTON’S SECOND LAW OF MOTION The relationship among force, acceleration and mass when combined and stated symbolically become a  F/m or F  ma Newton’s Law may be expressed in equation form as F = ma

NEWTON’S THIRD LAW (LAW OF ACTION AND REACTION) The third law of motion consider the way forces act against each other. If a book lying on a table which exerts a downward force on table, and because the book is stationary another equal and opposite force must be acting on it.

NEWTON’S THIRD LAW (ACTION AND REACTION) Newton’s third law of motion states that for every action there is an equal and opposite reaction. or All forces occur in pairs, and these two forces are equal in magnitude and opposite in direction

UNDERSTANDING NEWTON’S THIRD LAW OF MOTION The downward force of the book on the table is balanced by an upward force of table on the book. The same is true when a person walks across a floor. The feet push back against the floor with the same magnitude as the floor pushes forward against the feet.