Newton laws

It is not about Sir Isaac Newton's law such as in Physic, but it's about motivation according Newton's Law.

Newton's laws of motion are three physical laws that form the basis for classical mechanics. They are:

1. In the absence of force, a body either is at rest or moves in a straight line with constant speed.
2. A body experiencing a force F experiences an acceleration a related to F by F = ma, where m is the mass of the body. Alternatively, force is equal to the time derivative of momentum.
3. Whenever a first body exerts a force F on a second body, the second body exerts a force −F on the first body. F and −F are equal in magnitude and opposite in direction.

Newton's First Law :

Newton's first law is also called the law of inertia. It states that if the vector sum of all forces (that is, the net force) acting on an object is zero, then the acceleration of the object is zero and its velocity is constant. Consequently:

• An object that is not moving will not move until a force acts upon it.
• An object that is moving will not change its velocity until a net force acts upon it.

There is a class of frames of reference (called inertial frames) relative to which the motion of a particle not subject to forces is a straight line

Newton's Second Law:

Newton's second law states that the force applied to a body produces a proportional acceleration; the relationship between the two is

The second law can also be shown to relate the net force and the momentum p of the body:

Therefore, Newton's second law also states that the net force is equal to the time derivative of the body's momentum:

Impulse

An impulse I occurs when a force F acts over an interval of time Δt, and it is given by:

Since force is the time derivative of momentum, it follows that

This relation between impulse and momentum is closer to Newton's wording of the second law.

Impulse is a concept frequently used in the analysis of collisions and impacts.


Newton's Third Law(law of reciprocal actions):

''To every action there is always an equal and opposite reaction: or the forces of two bodies on each other are always equal and are directed in opposite directions''.

Action Force = Reaction Force

Importance and range of validity

Newton's laws were verified by experiment and observation for over 200 years, and they are excellent approximations at the scales and speeds of everyday life. Newton's laws of motion, together with his law of universal gravitation and the mathematical techniques of calculus, provided for the first time a unified quantitative explanation for a wide range of physical phenomena.

These three laws hold to a good approximation for macroscopic objects under everyday conditions. However, Newton's laws (combined with Universal Gravitation and Classical Electrodynamics) are inappropriate for use in certain circumstances, most notably at very small scales, very high speeds (in special relativity, the Lorentz factor must be included in the expression for momentum along with rest mass and velocity) or very strong gravitational fields. Therefore, the laws cannot be used to explain phenomena such as conduction of electricity in a semiconductor, optical properties of substances, errors in non-relativistically corrected GPS systems and superconductivity. Explanation of these phenomena requires more sophisticated physical theory, including General Relativity and Relativistic Quantum Mechanics.

In quantum mechanics concepts such as force, momentum, and position are defined by linear operators that operate on the quantum state; at speeds that are much lower than the speed of light, Newton's laws are just as exact for these operators as they are for classical objects. At speeds comparable to the speed of light, the second law holds in the original form F = dp/dt, which says that the force is the derivative of the momentum of the object with respect to time, but some of the newer versions of the second law (such as the constant mass approximation above) do not hold at relativistic velocities.