Physics deals with the study of natural phenomena .To approach the subject quantitatively,it is essential to male measurements.For example,we know that the earth rotates not only about its own axis but also revolves around the sun.What is the period of rotation of the earth about its own axis ?What is the period of revolution of the earth around the sun?To answer these questions,we have to make measurements.
A physical quantity is that which can be measured and expressed in unit directly or indirectly.Mass, length, time, density, temperature, etc are some examples of physical quantities.Sorrow, happiness, sadness, etc cannot be measured .So, they are not physical quantities.Without measurement, we cannot find the exact value of any physical quantity.
For the measurement of any physical quantity, we need a fixed quantity as a standard quantity.The measurement of unknown quantity can be done by comparing it with a standard quantity of the same kind.Thus, the process of comparison of an unknown quantity with a known standard quantity is called measurement.
Importance of measurement
1.Measurement is essential in selling and buying goods and commodities.
2.It is essential in performing scientific experiments to establish truth about a physical phenomenon.
3.It is required for global understanding of the quantity of a substance.
4.It is essential in performing experiment for making our daily foods.
5.Measurement of the medicine is a must in the treatment of diseases.
Fundamental and derived quantity
Those physical quantities, which can neither be derived from others nor be further resolved into other simpler quantities, are called fundamental quantities.
For example,length of a body is a fundamental quantity as it cannot be expressed in-terms of other quantities.How many kilograms equal 1 m?It does not make any sense.Length is not dependent on mass.Length, mass, time, electric current, temperature, intensity of light and amount of substance are the example of fundamental quantities.
Those physical quantities, which depend on two or more fundamental quantitise or power of fundamental quantity are called derived quantities.Area is a derived quantity.Since, area=length * breadth, it depends on two power of length (i.e. l square).
Similarly,density is also a derived quantity as density depends am mass (m) and three power of length (i.e. l cube).Volume, pressure, force, speed, acceleration, etc, are some other examples of derived quantities.
Friday, May 20, 2016
Thursday, May 19, 2016
Earth's orbit
Earth's circle is the way in which the Earth goes around the Sun. The normal separation between the Earth and the Sun is 149.60 million kilometers (92.96 million miles) and a complete circle happens at regular intervals (1 sidereal year), amid which time Earth voyages 940 million kilometers (584 million miles).Earth's circle has an unpredictability of 0.0167. Earth's orbital movement gives an evident development of the Sun regarding different stars at a rate of around 1° every day (or a Sun or Moon width at regular intervals) eastbound as seen from Earth.Earth's orbital rate midpoints around 30 km/s (108,000 km/h; 67,000 mph), which is sufficiently quick to cover the planet's measurement in seven minutes and the separation to the Moon in four hours.
Seen from a vantage point over the north shafts of both the Sun and the Earth, the Earth would seem to rotate in a counterclockwise bearing about the Sun. From the same vantage point, both the Earth and the Sun would seem to turn in a counterclockwise course about their particular tomahawks.
History of study
Heliocentrism:
Heliocentrism is the investigative model which at first put the Sun at the motivation behind converging of the Solar System and put the planets, including Earth, in its circle. Verifiably, heliocentrism is against geocentrism, which put the Earth at within. Aristarchus of Samos starting now proposed a heliocentric model in the third Century BC. In the sixteenth century, Nicolaus Copernicus' De revolutionibus showed a full discuss a heliocentric model of the universe also as Ptolemy had shown his geocentric model in the second century. This 'Copernican change' picked the issue of planetary retrograde progression by forcefulness that such change was just seen and clear. "In spite of the way that Copernicus' critical book...had been printed over a century earlier, the Dutch mapmaker, Joan Blaeu was the significant mapmaker to join his component heliocentric theory into an aide of the world."
Influence on earth
Season:
By ideals of Earth's urgent tilt a great part of the time known as the obliquity of the ecliptic,the slant of the Sun's heading in the sky as seen by a spectator on Earth's surface differentiations through the scope of the year. For a passerby at a northern augmentation, when the north shaft is tilted toward the Sun the day keeps going longer and the Sun seems, by all accounts, to be higher in the sky. This outcomes in additionally sizzling run of the mill temperatures, as more sun organized radiation achieves the surface. Right when the north post is tilted far from the Sun, the backwards is significant and the air is by and large cooler. Over the Arctic Circle, an uncommon case is come to in which there is no sunshine at all for part of the year. This is known as a polar night. This grouping in the climate in context of the heading of the Earth's middle point tilt results in the seasons.
Seen from a vantage point over the north shafts of both the Sun and the Earth, the Earth would seem to rotate in a counterclockwise bearing about the Sun. From the same vantage point, both the Earth and the Sun would seem to turn in a counterclockwise course about their particular tomahawks.
History of study
Heliocentrism:
Heliocentrism is the investigative model which at first put the Sun at the motivation behind converging of the Solar System and put the planets, including Earth, in its circle. Verifiably, heliocentrism is against geocentrism, which put the Earth at within. Aristarchus of Samos starting now proposed a heliocentric model in the third Century BC. In the sixteenth century, Nicolaus Copernicus' De revolutionibus showed a full discuss a heliocentric model of the universe also as Ptolemy had shown his geocentric model in the second century. This 'Copernican change' picked the issue of planetary retrograde progression by forcefulness that such change was just seen and clear. "In spite of the way that Copernicus' critical book...had been printed over a century earlier, the Dutch mapmaker, Joan Blaeu was the significant mapmaker to join his component heliocentric theory into an aide of the world."
Influence on earth
Season:
By ideals of Earth's urgent tilt a great part of the time known as the obliquity of the ecliptic,the slant of the Sun's heading in the sky as seen by a spectator on Earth's surface differentiations through the scope of the year. For a passerby at a northern augmentation, when the north shaft is tilted toward the Sun the day keeps going longer and the Sun seems, by all accounts, to be higher in the sky. This outcomes in additionally sizzling run of the mill temperatures, as more sun organized radiation achieves the surface. Right when the north post is tilted far from the Sun, the backwards is significant and the air is by and large cooler. Over the Arctic Circle, an uncommon case is come to in which there is no sunshine at all for part of the year. This is known as a polar night. This grouping in the climate in context of the heading of the Earth's middle point tilt results in the seasons.
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