PHYSICS

Newton's First Law

An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. This is known as the law of inertia.


Newton's Second Law

A force 'F' acting on a body gives it an acceleration 'a' which is in the direction of the force and has magnitude inversely proportional to the mass 'm' of the body: 

F = ma


Newton's Third Law

Whenever a body exerts a force on another body, the latter exerts a force of equal magnitude and opposite direction on the former. This is known as the weak law of action and reaction.


Strong Law of Action and Reaction

For every action force, there is a corresponding reaction force which is equal in magnitude and opposite in direction. Furthermore, the forces are central forces, i.e., they act along the line joining the particles.


Wave-Particle Duality

Microparticles, electrons, protons, photons, atoms and so forth, propagate as if they were waves, and exchange energy as if they were particles. That's the Wave-Particle duality.


Quantum Randomness

It appears that identical particles in identical situations need not to behave identically. That is the essence of quantum randomness.


Conservation of Energy

If the forces acting on a particle are conservative so that there exists a function V(r) such that

F = - V(r)

then the total energy

E = K + U

given as the sum of kinetic energy (often defined informally as energy of motion) and potential energy (often defined informally as energy at rest) is a constant.


The First Law of Thermodynamics

The first law of thermodynamics is a consequence of conservation of energy and requires that a system may exchange energy with the surroundings strictly by heat flow or work. Therefore, for change in energy dE, heat change , work done dW,

dE = dQ - dW


The Second Law of Thermodynamics

The second law of thermodynamics prohibits the construction of a perpetual motion machine "of the second kind." There are two usual statements of this law. Kelvin's formulation states that it is impossible for a system operating in a cycle and in contact with one thermal reservoir to perform positive work in the surroundings. Clausius's formulation states that it is impossible for a system operating in a cycle to produce positive heat flow from a colder body to a hotter body.

Two important consequences of the second law are the existence of a new state variable, the entropy S, and the theorem

dQ T dS

where dQ is the heat change, dT is the temperature change, and dS is the change in entropy.


The Third Law of Thermodynamics

As temperature goes to 0, the entropy S approaches a constant . Furthermore, it guarantees that the entropy of a pure, perfectly crystalline substance is 0 if the absolute temperature is 0.


Zeroth Law of Thermodynamics

If two systems are in thermal equilibrium with a third system, then they must be in thermal equilibrium with each other.


Uncertainty Principle

A quantum mechanical principle due to Werner Heisenberg (1927) that, in its most common form, states that it is not possible to simultaneously determine the position and momentum of a particle. Moreover, the better position is known, the less well the momentum is known (and vice versa). The principle is sometimes known as the Heisenberg uncertainty principle, and can be stated exactly as

Dx Dpx = h/2p


where Dx is the uncertainty in position, Dpx is the uncertainty in momentum, and h in h/2p is Planck's constant; h = 6.6262 * 10-34 [J s].