KERALA PSC / PHYSICS / GRAVITATION / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

 

KERALA PSC / PHYSICS / GRAVITATION / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

KERALA PSC / PHYSICS / GRAVITATION / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

·      Force of attraction between any two bodies in this universe is known as gravitation.

·      The attractive force of earth, or other celestial body, on an object is called gravity

·      The earth attracts everybody towards its centre. The acceleration with which the freely falling bodies are attracted towards the earth is called the acceleration due to gravity(g).

Value of g = 9.8 m/s²

·      The value of ‘g’ is independent of the nature and size of the bodies. It does not depend upon the nature of medium between the two bodies.

·      The value of g at the centre of earth is zero

·      The acceleration due to gravity is maximum on Jupiter and minimum on planet Mercury.

·      The value of g is very high at polar region

·      The value of g is very small at equatorial region

·      The weight of a substance is zero at the centre of earth. As the mass of the substances increases the gravitational force between them also increases.

·      The weight of a body in earth is very high in the polar region and low in the equatorial region.

·      The weight of a body on the moon will be less than its weight on the earth. This is so because the mass of the moon is 1/81 of the mass of the earth its radius is 1/3.66 of the radius of the earth. Therefore, the acceleration due to gravity experienced on the moon will be less than the acceleration due to gravity experienced on the earth. This will be about 1/6 g.

·      On the moon an astronaut cannot drink lemonade with the help of a straw because there is no atmosphere on the moon.

·      The mass of a body which determines the gravitational force of attraction due to earth is called gravitational mass.

·      Escape velocity is the minimum speed which a spacecraft must have to escape from the earth’s gravitational force. It is 7 miles/s. (or 11.2 km/s)

·      Escape velocity for moon is 2.4 km/s

·      The escape velocity does not depend on the mass of the body. It does not depend upon the angle of projection. For earth the escape velocity is 11.2 km/sec

·      In the absence of an effective force of gravity, bodies become weightless in artificial satellites.

·      Gravitational field is the space around a massive body in which gravitational force of attraction is felt.

·      Planets move slower along their orbits when they are farthest from the sun (at apogee) and they move faster along their orbits when they are nearest to the sun (at perigee)

·      Gravitation is responsible for keeping the Earth and the other planets in their orbits around the Sun; for keeping the Moon in its orbit around the Earth; for the formation of tides; for natural convection, by which fluid flow occurs under the influence of a density gradient and gravity; for heating the interiors of forming stars and planets to very high temperatures; and for various other phenomena observed on Earth.

·      The line on earth’s surface passing through the places having zero dip is called the magnetic equator. It passes through Thumba.

·      The orbit of a geostationary satellite is called as parking orbit

·      The relative velocity of geostationary satellite with respect to earth is zero

·      The orbital velocity does not depend on the mass of the body. It depends upon the mass and radius of the planet.

·      The orbit of a satellite must be circular and in the equatorial plane of the earth.

 

 

KERALA PSC / PHYSICS / GRAVITATION / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES