তাপ গতিবিদ্যার শূন্যতম সূত্র

আমাদের মনে হতেই পারে তাপ গতিবিদ্যার শূন্যতম সূত্রকে কেন শূন্যতম সূত্র বলা হয়।। প্রথম না দ্বিতীয় না শূন্যতম কেন? আচ্ছা বুঝলাম যে প্রথম এবং দ্বিতীয় সূত্র আছে তাই প্রথম না দ্বিতীয়ও না। কিন্তু তৃতীয় হতে দোষ কি ছিল? আমাদের অনেকেরই এমনটা মনে হতেই পারে। মনে হতেই পারে এটা ভুল। কিন্তু না, এটাই সঠিক। একে শূন্যতম সূত্র বলার কারণ হল, এটি ওই দুটি সুত্রের পরে আবিষ্কৃত হয়েছিল কিন্তু বিষয় বস্তু এবং বৈশিষ্ট্য এর দিক থেকে এটা ওই দুই সুত্রের চেয়ে মৌলিক ছিল। এতটাই মৌলিক যে এটি ওই দুই সুত্রের ভিত্তি বলে মনে হয়েছিল। তাই একে তাপ গতিবিদ্যার শূন্যতম সূত্র বলা হয়।। আশা করি এরপর আর কোনও কনফিউশন থাকবে না। ধন্যবাদ।।

অনুরোধে এডমিন

পর্যায়ক্রমে সব অধ্যায়ভিত্তিক টপিক এর ওপর গুরুত্বপূর্ণ তথ্য বাংলায় দেওয়া হবে।। এর ওপর কাজ করা হচ্ছে।। ততক্ষণ পর্যন্ত অপেক্ষা করুন।। ধন্যবাদ।।

Gravitation
এতে মহাকর্ষ নিয়ে কিছু গুরুত্বপূর্ণ তথ্য আছে।।

Principle of Equivalence

Albert Einstein once said: “I was . . . in the patent office at Bern when all of a sudden a thought occurred to me: ‘If a person falls freely, he will not feel his own weight.’ I was startled. This simple thought made a deep impression on me. It impelled me toward a theory of gravitation.” Thus Einstein tells us how he began to form his general theory of relativity. The fundamental postulate of this theory about gravitation (the gravitating of objects toward each other) is called the principle of equivalence, which says that gravitation and acceleration are equivalent. If a physicist were locked up in a small box as in Fig. 13-18, he would not be able to tell whether the box was at rest on Earth (and subject only to Earth’s gravitational force), as in Fig. 13-18a, or accelerating through interstellar space at 9.8 m/s2 (and subject only to the force producing that acceleration), as in Fig. 13-18b. In both situations he would feel the same and would read the same value for his weight on a scale. Moreover, if he watched an object fall past him, the object would have the same acceleration relative to him in both situations.

My say

বন্ধুরা কেমন আছ সবাই? নিজের একটা ওয়েবসাইট খুললাম। সবার হেল্প চাই।

Newton’s law of Gravitation…

Newton at the age of twenty-three is said to have seen an apple falling down from tree in his orchid. This was the year 1665. He started thinking about the role of earth’s attraction in the motion of moon and other heavenly bodies. By comparing the acceleration due to gravity due to earth with the acceleration required to keep the moon in its orbit around the earth, he was able to arrive the Basic Law of Gravitation.

Hi, This is Shamim, going to start a physics based website, where you can get information about physics. Thank you all.

Properties of Gravitational Force.

(1) It is always attractive in nature while electric and magnetic force can be attractive or repulsive.
(2) It is independent of the medium between the particles while electric and magnetic force depend on
the nature of the medium between the particles.
(3) It holds good over a wide range of distances. It is found true for interplanetary to inter atomic
distances.
(4) It is a central force i.e. acts along the line joining the centres of two interacting bodies.
(5) It is a two-body interaction i.e. gravitational force between two particles is independent of the
presence or absence of other particles; so the principle of superposition is valid i.e. force on a particle due to
number of particles is the resultant of forces due to individual particles
While nuclear force is many body interaction
(6) It is the weakest force in nature : As F nuclear > F electromagnetic > F gravitational .
(7) The ratio of gravitational force to electrostatic force between two electrons is of the order of 43 10 ƒ{ .
(8) It is a conservative force i.e. work done by it is path independent or work done in moving a particle
round a closed path under the action of gravitational force is zero.
(9) It is an action reaction pair i.e. the force with which one body (say earth) attracts the second body
(say moon) is equal to the force with which moon attracts the earth. This is in accordance with Newton’s third
law of motion.

Kepler’s Laws

Johannes Kepler, a 29-year-old German, became one of Brahe’s assistants when he moved to Prague. Brahe trained his assistants to use instruments, such as those shown in Figure 7-1. Upon his death in 1601, Kepler inherited 30 years’ worth of Brahe’s observations. He studied Brahe’s data and was convinced that geometry and mathematics could be used to explain the number, distance, and motion of the planets. Kepler believed that the Sun exerted a force on the planets and placed the Sun at the center of the system. After several years of careful analysis of Brahe’s data on Mars, Kepler discovered the laws that describe the motion of every planet and satellite. Kepler’s first law states that the paths of the planets are ellipses, with the Sun at one focus. An ellipse has two foci, as shown in the Figure . Like planets and stars, comets also orbit the Sun in elliptical orbits. Comets are divided into two groups—long-period comets and short-period comets— based on orbital periods, each of which is the time it takes the comet to complete one revolution. Long-period comets have orbital periods longer than 200 years, and short-period comets have orbital periods shorter than 200 years. Comet Hale-Bopp, with a period of 2400 years, is an example of a long-period comet. Comet Halley, with a period of 76 years, is an example of a short-period comet. Kepler found that the planets move faster when they are closer to the Sun and slower when they are farther away from the Sun. Thus, Kepler’s second law states that an imaginary line from the Sun to a planet sweeps out equal areas in equal time intervals, as illustrated in the Figure Kepler also found that there is a mathematical relationship between periods of planets and their mean distances away from the Sun. Kepler’s third law states that the square of the ratio of the periods of any two planets revolving about the Sun is equal to the cube of the ratio of their average distances from the Sun. Thus, if the periods of the planets are TA and TB, and their average distances from the Sun are rA and rB, Kepler’s third law can be expressed as follows Kepler’s Third Law The squared quantity of the period of object A divided by the period of object B, is equal to the cubed quantity of object A’s average distance from the Sun,
divided by object B’s average distance from the Sun.

Planetary motion and gravitation

Since ancient times, the Sun, Moon, planets, and stars had been
assumed to revolve around Earth. Nicholas Copernicus, a Polish
astronomer, noticed that the best available observations of the movements
of planets and stars did not fully agree with the Earth-centered model. The
results of his many years of work were published in 1543, when
Copernicus was on his deathbed. His book showed that the motion of
planets is much more easily understood by assuming that Earth and other
planets revolve around the Sun.
Tycho Brahe was born a few years after the death of Copernicus. As a boy
of 14 in Denmark, Brahe observed an eclipse of the Sun on August 21,
1560, and vowed to become an astronomer.
Brahe studied astronomy as he traveled throughout Europe for five
years. He did not use telescopes. Instead, he used huge instruments that
he designed and built in his own shop on the Danish island of Hven. He
spent the next 20 years carefully recording the exact positions of the planets
and stars. Brahe concluded that the Sun and the Moon orbit Earth and that
all other planets orbit the Sun.