According to Bernoulli’s theorem, the sum total of these three kinds of energies, kinetic energy, potential energy and pressure energy remains constant along a streamline in a steady flow of an ideal fluid. That is
P + ρv²/2 + ρgh = constant
Johannes Kepler used empirical observations, and sophisticated calculations to arrive at the famous Kepler’s laws of planetary motion, published in 1609 and 1619. What is particularly significant about Kepler’s laws is that they challenged the prevailing world’s view, with the Earth in the center of the universe (a geocentric theory) and the Sun and all the planets and stars orbiting around it, just as the Moon does .
The quantities which do not depend upon other quantities for their complete definition are known as fundamental quantities.
There are 7 fundamental quantities .
eg- length , mass , current etc .
and Derived quantities are those quantities that can be expressed in terms of fundamental quantities .
eg- density , velocity , momentum , energy etc .
Physical quantities can be measured in a proper unit and it has a numerical value . Physical quantities are verified scientifically and help us to define laws of physics .
eg. mass, amount of substance, length, time, temperature, electric current, light intensity, force, velocity, density, momentum , energy .
And Non- Physical quantities are those quantities that can not be measured by any device , does not have unit or magnitude themselves . Sometimes these quantities can be compared to each other .
eg. Rudeness, Love , Happiness, Sadness , Proudness, Respect, Pride, Hate, Angry, Loyalty and Stupidity .
The continuity equation is a mathematical expression of the law of conservative of mass in fluid dynamics .
This equation defines the steady flow of a fluid in a tube. It states that if flow of a fluid is steady then the mass of the fluid entering per second at one end is equal to the mass of fluid leaving per second at the other end .
Barometer is a device used to measure atmospheric pressure . In principle , any liquid can be used to fill the Barometer, but mercury is the substance of choice because its high density makes possible an instrument of reasonable size . It uses liquid mercury to predict the weather by tracking atmospheric pressure changes resulting from the movement of warm and cold weather systems .
We know that in an statics fluid pressure in horizontal direction will be constant because of equi-pressure surface but in case of vertical Variation it’s Vary .If the weight of the fluid can be neglected, the pressure in a fluid is the same throughout its volume. But often the fluid’s weight is not negligible and under such condition pressure increases with increasing depth below the surface .
dp/dy = ρg . ( This is the general expression of variation of pressure with depth ) .