Newton’s three laws of motion are the 3 physical laws, these laws of motion laid the foundation for classical
mechanics. These laws explain the relation between forces and the body on which these forces acted upon.
Newton’s first law of motion gives the qualitative definition of force, Newton’s second law of motion gives the quantitative measure of the force, while Newton’s third law of motion asserts that a single isolated force does not exist.
To learn in detail about these laws click the list which is given below:
- Newton’s first law of motion
- Newton’s second law of motion
- Newton’s third law of motion
- Different types of motion in physics with examples
For centuries the problem of motion and its causes was a central theme of natural philosophy, an early name for what we call physics. It was not until the time of Galileo and Newton, however, that dramatic progress was made. Isaac Newton, born in England in the year of Galileo’s death, is the principal architect of classical mechanics. He carried to full fruition the ideas of Galileo and others who preceded him. His three laws first presented (in 1686) in his Philosophiae Naturalis Principia Mathematica, usually called the Principia. In his Principia Newton stated the three fundamental laws of motion, which are the basis of Newtonian mechanics.
Before Galileo’s time, most philosopher’s thought that some influence or “force” was needed to keep a body moving. They thought that a body was in its “natural state” when it was at rest. For a body to move in a straight line at a constant speed, for example, they believed that some external agent had to continually propel it; otherwise, it would”naturally” stop moving.
If we wanted to test these ideas experimentally we would first have to find a way to free a body from all influences of its environment or from all forces. This is hard to do, but in certain cases, we can make the forces very small. If we study the motion as we make the forces smaller and smaller, we shall have some idea of what motion would be like if the external forces were truly zero.
Let us place our test body, say a block, on a rigid horizontal plane. If we let the block slide along this plane, we note that it gradually slows down and stops. This observation was used, in fact, to support the idea that motion stopped when the external force, in this case, the hand initially pushing the block, was removed.
We can argue against this idea, however, by reasoning as follows. Let us repeat our experiment, now using a smoother block and a smoother plane and providing a lubricant. We note that the velocity decreases more slowly than before.
Let us used still smoother blocks and surfaces and better lubricants. We find that the block decreases in velocity at a slower and slower rate and travels farther each time before coming to rest. You may have experimented with an air track, on which objects can be made to float on a film of the air; such a device comes close to the limit of no friction, as even a slight tap on one of the gliders can send it moving along the track at a slow and almost constant speed.
We can now extrapolate and say that if all friction could be eliminated the body would continue indefinitely in a straight line with constant speed. An external force is needed to set the body in motion, but no external force is needed to keep a body moving with constant velocity.
It is difficult to find a situation in which no external force acts on a body. The force of gravity will act on an object on or near the earth, and resistive forces such as friction on air resistance oppose the motion on the ground or in the air.
Fortunately, we need not go to the vacuum of distant space to study motion free of external force, because, as for as the overall transnational motion of the body is concerned, there is no distinction between a body on which no external force acts and a body on which the sum or resultant of all the external force is zero.
We usually refer to the resultant of all the forces acting on the body as the “net” force. For example, the push of our hand on the sliding block can exert a force that contracts the force of friction on the block, and an upward force of the horizontal plane contracts the force of gravity. The net force on the block can then be zero, and the block can move with constant velocity.
This principle was adopted by Newton as the first of his three laws of motion:
Newton’s laws marked a revolution within the field of physics. They formed the foundations of dynamics (part of the mechanics that studies movement according to the forces that originate it). Furthermore, by combining these principles with the law of universal gravitation, the laws of the German astronomer and mathematician, Johannes Kepler, on the motion of planets and satellites could be explained.
Newton’s First Law – The Inertia Principle
Newton’s first law states that a body only varies its speed if an external force acts on it. Inertia is the tendency of a body to continue as it is.
According to this first law, a body cannot change its state by itself; for it to come to rest (initial velocity: 0) or uniform rectilinear motion, it is necessary for some force to act on it.
Therefore, if no force is applied and a body is in a state of rest, it will remain so; if a body was in motion, it will continue to be in uniform motion at a constant speed.
For example, A man leaves his car parked outside his house. No force acts on the car. The next day, the car is still there.
Newton extracts the idea of inertia from the Italian physicist, Galileo Galilei ( Dialogue on the two great systems of the world -1632).
Newton’s Second Law – The Fundamental Principle of Dynamics
Newton’s second law states that there is a relationship between the force exerted and the acceleration of a body. This relationship is direct and proportional, that is, the force exerted on a body is proportional to the acceleration it will have.
For example, Juan is 10 years old. The more force Juan applies when kicking the ball, the better the chance that the ball will cross half the court.
Acceleration depends on the magnitude, direction, and direction of the resulting force, and the mass of the object.
- It can help you: How is the acceleration calculated?
Newton’s Third Law – The Principle of Action and Reaction
Newton’s third law states that when one body exerts a force on another, the latter responds with a reaction of equal magnitude and direction but in the opposite direction. The force exerted by the action corresponds to a reaction.
For example: When a man stumbles over a table, he will receive from the table the same force that he applied with the blow.
Examples of Newton’s First Law
- The driver of the automobile brakes abruptly and, by inertia, shoots forward.
- The stone in the ground is in a]the state of rest.
- The bicycle stored ten years ago in a loft comes out of its inertia when the child decides to use it.
- The marathoner continues to run several meters beyond the finish line due to the law of inertia of his career.
- See more examples in Newton’s First Law
Examples of Newton’s second law
- A lady teaches two children to ride a bicycle: one 4-year-old and the other 10-year-old, so that they arrive at the same place, they will have to exert more force when pushing the 10-year-old boy because his weight is greater.
- A car needs a certain amount of horsepower to be able to drive on the road.
- Pushing a broken down car among more people will make the car move faster.
- See more examples in: Newton’s Second Law
Examples of Newton’s third law
- If one billiard ball hits another, the second will move with the same force as the first.
- A child wants to jump to climb a tree (reaction), he must push the ground to propel himself (action).
- A man deflates a balloon; the force with which the air comes out causes the balloon to move from one side to the other.
- See more examples in: Newton’s third law