Keplers’s Laws of Planetary Motion, Kepler's Law, Law of Orbits, Law of Areas, Law of periods

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  Keplers’s Laws of Planetary Motion: 1 st law ( Law of Orbits ): Every planet moves around the sun in elliptical orbit with the sun at one of the foci of the elliptical orbit. 2 nd   law ( Law of Areas): The line joining the planet to the sun sweeps over equal areas in equal intervals of time.                                                             Area of SAB = Area of SCD  2 nd   law tells us that a planet does not move with constant speed around the sun. It speeds up while approaching the nearest point called ‘ perigee’ and slows downs while approaching the farthest point called ‘ apogee’. therefore, distance covered on the orbit with in the given interval of time at perigee is greater than that at apogee such that areas swept are equal. 3 rd Law ( Law of periods): The square of the time periods of revolution of...
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Coulomb's Law definition and derivation

Definition:- The magnitude of the electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them.

The law was first published in 1785 by French physicist Charles-Augustin de Coulomb, and was essential to the development of the theory of electromagnetism, maybe even its starting point, because it was now possible to discuss quantity of electric charge in a meaningful way.

Coulomb's Law Derivation:-


We can show it with the following explanation. Let’s say that there are two charges q1 and q2. The distance between the charges is ‘r’, and the force of attraction/repulsion between them is ‘F’. Then

F  ∝ q1q2   ••••••• (1)
F  ∝  1/r2   •••••••(2)
By the equation no. 1 and 2

F  = k q1q2/ r2
where k is proportionality constant and equals to 1/4 π ε0.

where ε0 is absolute permittivity of free space. Value of this constant in vacuum is 8.85×10−12C2/Nm2. If we put the value of ε0 in above equation for k we find



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