Galileo made a great advance in the understanding of motion when he discovered the principle of inertia: if an object is left alone, it continues to move with a constant velocity in a straight line if it was originally moving, or it continues to stand still if it was just standing still. The next thing which was needed was a rule for finding how an object changes its speed if something is affecting it. Relations between the forces acting on a body and the motion of the body were first formulated by Isaac Newton. The study of that relation, as Newton presented it, is called Newtonian mechanics.
Newton’s laws of motion are three physical laws that together laid the foundation for classical mechanics. Newton postulated three laws: The first law is known as principle of inertia. To explain with a practical example, if you are driving a car at a very high speed and hit something, like a brick wall or a tree, the car will come to an instant stop, but you will keep moving forward. This is why cars have air-bags, to protect you from smashing into the windscreen. Second law, which asserts that the motion of an object is changed by forces in this way: the time-rate-of-change of a quantity called momentum is proportional to the force and the third law describes the underlying symmetry of applied forces. Like the air that flies up a balloon when the air rushes out of it.
The Second law gave a specific way of determining how the velocity changes under different influences called forces. Force can be described as a push or pull on the object. The force is said to act on the object to change its velocity, which is described as acceleration of the object. For example, when a car accelerates, a force from the track acts on the rear tires to cause the car’s acceleration.
These three laws form the foundation of Newtonian mechanics. The bodies of large objects in motion, such as orbiting moons or planets in Gravitation, or ordinary objects on Earth’s surface, such as moving vehicles or speeding bullets could be studied through Newton’s law of motion. The motions of pendulums, oscillators of spring mass systems in SHM, could all be analysed completely using Newton’s laws.
The motion of a body falling down through the atmosphere or calculating the required velocity of ejected gases for a rocket being launched into space are excellent examples of real life applications of Newton’s laws. Orbital velocity of a geostationary satellite is determined based on centripetal force required for its circular motion. The sea animals like squid and octopus uses newtons third law to propel themselves in sea.
“Newton’s laws of Motion” is one of the basic and important chapters of Mechanics in the Physics syllabus of CBSE, IIT JEE, BITSAT, AIPMT and other entrance examinations as it fetches 2-3 questions in most of the engineering and medical examinations. The problems based on this are very easy and can be solved by learning few concepts.
Motion of a body is described in two parts I) Cause of motion: dynamics and II) Effect of cause: Kinematics. The equations of motion are used to describe the motion of object under effect of applied forces. The velocity, force, acceleration, and momentum have both a magnitude and a direction associated with them. Prior knowledge on vectors is required in writing equations of motion.
The applications of newton’s laws are not limited to classical physics. In modern physics as well the dynamics concepts are used in studying the motion of electrons around the nucleus. The velocity and acceleration of a charged particle in electromagnetic field are determined using II law of motion, making it a prerequisite for most of the important chapters in physics.