The success and the fame that Newton earned was to a large extent due to his discovery of the three principles of motion that proved the important foundation slabs upon which came up the edifice of modern physics. The motions were there ever and man was very much getting their benefit but no one was able to define them in principle forms. Whatever little research had been done before Newton in this respect had no scientific validity or certification. But Newton was destined to unravel the mystery of natural science. About the achievements of Newton English poet Alexander Pope wrote:
“Nature and nature’s laws lay hid in night,
God said let Newton be’ and all was light”
In his text Alexander Pope expressed the sentiment that Newton was born to uncover the hidden mysteries of nature. What Newton discovered set the world of physics in motion to conquer the ever new frontiers of mechanics and space. Till the arrival of Newton the man only knew that life was a motion and motion was life. But he had no idea what exactly it was in definitions and what laws governed it. Without knowledge he could not work out mechanical application of motion and machines were metallic rig-ups that operated on motions. With his natural mind Newton had studied the phenomena of natural forces. His mind wondered why rules of nature apply or work uniformly in all situations? Behind that uniform application what laws or principles worked?
FIRST LAW OF MOTION—INERTIA
If a mass or an object is lying inert (motionless) it will remain inert if external force does not give it motion or activeness. A stone lying on the ground remains motionless in a state of inertia. Similarly if the force of wind carries a dry leaf lying on the ground away we can say it has lost inertia. An inert mass does not lose its motionless state until a force greater than its inertia does not act on it. Similarly a mass in motion will remain in motion unless some external force does intervene to slow it down or break its motion totally. In space the satellites stay in motion due to the law of inertia. Once given motion they stay orbiting at the same speed.
SECOND LAW OF MOTION—VELOCITY
A mass (or object) subjected to a (F) force gains velocity or Acceleration. If a mass in inertia is to be moved a (F) force has to be applied, A force so applied for a specific time results in momentum which is the speed of the movement of that mass. The equation of the second Law of Motion of Newton is :
Here mass (m) is inert and velocity is (a) acceleration i.e. Through r=dv/dt gets us to Newton’s famous equation F=ma
THIRD LAW OF MOTION—ACTION & REACTION
The third law of Newton is ‘Action and Reaction are Equal and Opposite’. If a mass is activated through application of force it generates reaction. For every action there is reaction, equal and opposite.
The following examples should explain it:
If a man pushes large rock lying on the ground with steel rod then the force of the rod will trigger reaction equally on the man and the stone. The rock will move forward and the man will get pushed backwards. The forwards movement of the rock is action and the push back of the man is reaction. It should be noted that to get the rock move forward bigger force than its inertia shall be required.
Another ideal example is that of gun and bullet. The gun butt is held tight against the right shoulder front to absorb the backward reaction of the gun when it is fired and the bullet shoots forward. In this third law Newton has considered the friction as the aspect of inertia in unit form, this action needs to have worked up greater force than the combined force of the inertia and friction.
One more example can be given with a ball. If a ball is rolled away on the ground it stops after travelling some distance due to the resistance of the friction. The speed of the ball or distance covered can be less or more depending upon the quantum of the force applied. If a ball is let go on a slope it rolls down and stops only when it reaches level ground or bottom of the slope. There is little friction and the slope works as force provider.
