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.
Wednesday, May 18, 2016
Events in the orbit
By galactic custom, the four seasons are supervised by the solstices the two centers in the Earth's circle of the most astounding tilt of the Earth's inside point, towards the Sun or a long way from the Sun and the equinoxes the two centers in the Earth's circle where the Earth's tilted turn and a wonderful line pulled in from the Earth to the Sun are totally in chat to each other. The solstices and equinoxes separate the year up into four around a sensibility of. In the northern part of the globe winter solstice happens for the most part December 21; summer solstice is close June 21; spring equinox is around March 20; and harvest time equinox is about September 23.The effect of the Earth's inside point tilt in the southern side of the equator is the retrogressive in the northern side of the equator, thusly the seasons of the solstices and equinoxes in the southern side of the equator are the backward of those in the northern side of the equator (e.g. the northern summer solstice is meanwhile as the southern winter solstice).
In present day times, Earth's perihelion happens around January 3, and the aphelion around July 4 (for various periods, see precession and Milankovitch cycles). The making Earth-Sun division results in a change of around 6.9% all around sun filled criticalness satisfying the Earth at perihelion concerning aphelion. Since the southern side of the equator is tilted toward the Sun at about the same time that the Earth satisfies the closest approach to manage the Sun, the southern side of the equator gets to some degree more centrality from the Sun than does the northern through the level of a year. Interestingly, this effect is fundamentally less vital than the total centrality change in context of the principal tilt, and most of the riches immensity is eaten up by the more raised measure of water in the southern side of the equator.
The Hill circle (gravitational great 'ol designed reach) of the Earth is around 1,500,000 kilometers (0.01 AU) in degree, or around 4 times the general pack to the moon.This is the best division at which the Earth's gravitational effect is more grounded than the more cleared Sun and planets. Objects turning around the Earth must be inside this degree, else they can influence the opportunity to be unbound by the gravitational impediment of the Sun.
In present day times, Earth's perihelion happens around January 3, and the aphelion around July 4 (for various periods, see precession and Milankovitch cycles). The making Earth-Sun division results in a change of around 6.9% all around sun filled criticalness satisfying the Earth at perihelion concerning aphelion. Since the southern side of the equator is tilted toward the Sun at about the same time that the Earth satisfies the closest approach to manage the Sun, the southern side of the equator gets to some degree more centrality from the Sun than does the northern through the level of a year. Interestingly, this effect is fundamentally less vital than the total centrality change in context of the principal tilt, and most of the riches immensity is eaten up by the more raised measure of water in the southern side of the equator.
The Hill circle (gravitational great 'ol designed reach) of the Earth is around 1,500,000 kilometers (0.01 AU) in degree, or around 4 times the general pack to the moon.This is the best division at which the Earth's gravitational effect is more grounded than the more cleared Sun and planets. Objects turning around the Earth must be inside this degree, else they can influence the opportunity to be unbound by the gravitational impediment of the Sun.
Tuesday, May 17, 2016
Diurnal and annual motion of the earth
The earth move round on its axis as well as in its orbit around the sun.The motion of the earth on its axis is called diurnal motion and a complete round on its axis is called a rotation.The earth takes about 24 hours (23 hr 59 min and 4.09 s) to complete one rotation.The motion of the earth in its orbits is called annual motion and a complete round around the sun is called a revolution.The revolution of the earth has a direct concern with the change in seasons and varying length of day and night.The rotation of the earth causes day and night on the earth.The earth takes about 365 days (365 days, 6 hr, 9 min and 9.54 s) to complete one revolution.
The axis of the earth is inclined to the plane of ecliptic at an angle of 66.5 degree.It causes different seasons and varying lengths of day and night.If the axis were perpendicular to this plane,all parts of the earth would have equal day and nights at all times of the year.
Day and night: an effect of the rotation of the earth
Day and night on the earth occur due to its rotation.when the earth rotates on it axis,only one portion of its surface faces the rays of the sun and experiences day.The other portion which is always from the sun's ray will be in darkness which experiences night.
To understand better about the cause of day and night, place a globe or ball as the earth in a dark room and use a flash of light or a table lamp representing the sun. Do you see all the parts of the globe facing light?
When the earth rotates eastwards,every part of the earth's surface will be exposed to the sun at some time or the other.The part of the earth's surface that emerges from darkness into the sun's rays experiences sunrise.Later, when it is gradually obscured from the sun's rays,it experiences sunset.
The axis of the earth is inclined to the plane of ecliptic at an angle of 66.5 degree.It causes different seasons and varying lengths of day and night.If the axis were perpendicular to this plane,all parts of the earth would have equal day and nights at all times of the year.
Day and night: an effect of the rotation of the earth
Day and night on the earth occur due to its rotation.when the earth rotates on it axis,only one portion of its surface faces the rays of the sun and experiences day.The other portion which is always from the sun's ray will be in darkness which experiences night.To understand better about the cause of day and night, place a globe or ball as the earth in a dark room and use a flash of light or a table lamp representing the sun. Do you see all the parts of the globe facing light?
When the earth rotates eastwards,every part of the earth's surface will be exposed to the sun at some time or the other.The part of the earth's surface that emerges from darkness into the sun's rays experiences sunrise.Later, when it is gradually obscured from the sun's rays,it experiences sunset.
Friday, May 13, 2016
The earth in the universe
The universe
The universe has unlimited size and unknown shapes.All the existing things including different galaxies, constellations, planets, satellites, comets, meteors, meteorites, asteroids etc.constitute it.Our earth is a planet, which is a member of the solar system.The solar system is situated in a galaxy called milky way.The milky way is a medium size galaxy,which consists of about 150 billions of stars. Astonomers believes that there are about 10 power 12 such galaxies in the univers. Now you can imagine that how hug the universe is.Because of its so huge and unlimited size,the distance between two heavenly bodies is inconvenient to measure in metres and kilometres. Hence, astronomical unit(AU), Light year(LY) and parsec are used to measure the distance in the universe.
1 AU= 1.5*10 power 11 m
1 LY= 9.46*10 power 15 m
1 Parsec = 3.26 Ly
Solar system
Only the sun is a known star, which has a group like solar family and only one planet the earth of it has suitable conditions for organisms to survive on it. The solar system consists of the sun and all the objects around it are influenced by its gravity.These objects include planets, dwarf planets and satellites. Countless other smaller objects such as meteroids (meteors and meteorites), and an electrically charged gas the sun. Drifting particles called interplanetary dust and an electrically charged gas known as plasma exist in the space of the solar system. Although solar system is huge, it is only a small part of a galaxy. The eight planets of the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
The international convention of astronomers held on 2006 in Prague of Czech Republic has removed the Pluto from the list of planets.A new definition of planet is also given by the convention. According to it:
1.A planet should have its own round orbit (elliptical) around the sun.
2.Its shap must be round.
3.Its orbit must not cross the orbit of other planets.
The Pluto fails to fulfill the last condition, due to which it is kept in the category of Dwarf planets.Eris and Ceres are also kept under this category.
In the solar system,the asteroids belt lies between the orbits of Mars and Jupiters.
The universe has unlimited size and unknown shapes.All the existing things including different galaxies, constellations, planets, satellites, comets, meteors, meteorites, asteroids etc.constitute it.Our earth is a planet, which is a member of the solar system.The solar system is situated in a galaxy called milky way.The milky way is a medium size galaxy,which consists of about 150 billions of stars. Astonomers believes that there are about 10 power 12 such galaxies in the univers. Now you can imagine that how hug the universe is.Because of its so huge and unlimited size,the distance between two heavenly bodies is inconvenient to measure in metres and kilometres. Hence, astronomical unit(AU), Light year(LY) and parsec are used to measure the distance in the universe.
1 AU= 1.5*10 power 11 m
1 LY= 9.46*10 power 15 m
1 Parsec = 3.26 Ly
Solar system
Only the sun is a known star, which has a group like solar family and only one planet the earth of it has suitable conditions for organisms to survive on it. The solar system consists of the sun and all the objects around it are influenced by its gravity.These objects include planets, dwarf planets and satellites. Countless other smaller objects such as meteroids (meteors and meteorites), and an electrically charged gas the sun. Drifting particles called interplanetary dust and an electrically charged gas known as plasma exist in the space of the solar system. Although solar system is huge, it is only a small part of a galaxy. The eight planets of the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
The international convention of astronomers held on 2006 in Prague of Czech Republic has removed the Pluto from the list of planets.A new definition of planet is also given by the convention. According to it:
1.A planet should have its own round orbit (elliptical) around the sun.
2.Its shap must be round.
3.Its orbit must not cross the orbit of other planets.
The Pluto fails to fulfill the last condition, due to which it is kept in the category of Dwarf planets.Eris and Ceres are also kept under this category.
In the solar system,the asteroids belt lies between the orbits of Mars and Jupiters.
Thursday, May 5, 2016
Force
Consider a pen is lying on a table.It continues to be lying on the table at the same position until someone displaces it to other position. From moving it, one has to either puss or pull it Such push or pull on a body i called force Thus,to bring a body into motion from the state of rest,any force has to act on it.
Consider a situation in which a ball is rolling on the ground. We observe that the ball finally stop after covering a certain distance.It will cover longer distance if the ground is made smoother.We can well assume that when the ground is perfectly smooth, the ball would continue moving forever in the same direction with a constant speed.It is the roughness of the surface that provides opposing force called friction,to stop the ball from moving.Thus,to bring a body into rest from the state of motion,force has to act on it in opposite direction of its motion.
Consider a very big stone at rest to which boy cannot move by pushing or pulling it.This means, the force exerted by the boy is insufficient to move the stone.Similarly, a moving body cannot be stopped if the applied force is insufficient.Only sufficient force can do this.A body having a small mass requires less force to move or to stop.
Thus, force is that push or pull on a body that changes or tends to change the state of rest or of uniform motion in a straight line.
Force acting on a body can do the following things:
1.It can change the speed of the body.
2.It can change the direction of motion of body.
3.It can change the shape and size of the body.
4.I t can change the position of the body.
The SI unit of force is newton(N).In CGS system,the unit of force is dyne.
1 Newton=100000 dynes.
Force is measured bu using a spring balance or a top pan balance.
Balanced and unbalanced forces
When a number of forces acting on a body do not change its state of rest or uniform motion in a straight line,the forces are said to be balanced forces.For example, in the game of tug of war,two teams pull a rope in opposite directions.When the two teams exert equal and opposite forces on the rope,the rope remains steady and does not move in any direction.It appears as if no force is acting on the rope.Thus, the two forces acting on the rope in this case are balanced forces.
When a number of forces acting on a body change its state of rest or uniform motion in a straight line,the forces are said to be unbalanced forces.For example,if we push a toy car towards east,it moves towards east.If it is pushed towards west,it moves towards west.This unbalanced force produces motion.
Inertia
The property of a body due to which it remains or tends to remain in the state of rest or uniform motion in a straight line unless an unbalanced force act on it, is called inertia.Only unbalanced force can change the state of rest of the state of motion and vice versa.Because of this property of the body,it opposes any change in its state of rest or of uniform motion in a straight line.
Consider a very big stone at rest to which boy cannot move by pushing or pulling it.This means, the force exerted by the boy is insufficient to move the stone.Similarly, a moving body cannot be stopped if the applied force is insufficient.Only sufficient force can do this.A body having a small mass requires less force to move or to stop.
Thus, force is that push or pull on a body that changes or tends to change the state of rest or of uniform motion in a straight line.
Force acting on a body can do the following things:
1.It can change the speed of the body.
2.It can change the direction of motion of body.
3.It can change the shape and size of the body.
4.I t can change the position of the body.
The SI unit of force is newton(N).In CGS system,the unit of force is dyne.
1 Newton=100000 dynes.
Force is measured bu using a spring balance or a top pan balance.
Balanced and unbalanced forces
When a number of forces acting on a body do not change its state of rest or uniform motion in a straight line,the forces are said to be balanced forces.For example, in the game of tug of war,two teams pull a rope in opposite directions.When the two teams exert equal and opposite forces on the rope,the rope remains steady and does not move in any direction.It appears as if no force is acting on the rope.Thus, the two forces acting on the rope in this case are balanced forces.
When a number of forces acting on a body change its state of rest or uniform motion in a straight line,the forces are said to be unbalanced forces.For example,if we push a toy car towards east,it moves towards east.If it is pushed towards west,it moves towards west.This unbalanced force produces motion.
Inertia
The property of a body due to which it remains or tends to remain in the state of rest or uniform motion in a straight line unless an unbalanced force act on it, is called inertia.Only unbalanced force can change the state of rest of the state of motion and vice versa.Because of this property of the body,it opposes any change in its state of rest or of uniform motion in a straight line.
Subscribe to:
Comments (Atom)