Among the planets, the acceleration due to gravity is minimum on the mercury. (iii) Law of period The square of the time period of revolution of planet around the sun is directly proportional to the cube semi-major axis of its elliptical orbit. These are (i) the gravitational force (ii) the electromagnetic force Each planet revolves around the sun in an elliptical orbit with the sun at one of the foci of the ellipse. Its value is constant and it never changes. SHARES. (ii) If V = vo then satellite revolves in circular path/orbit around earth. The value of G is independent of the nature and size of the bodies well as the nature of the medium between them. Hindi Physics. (d) Gravitational mass of a body is affected by the presence of other bodies near it. (vii) Newton’s third law of motion holds good for the force of gravitation. These satellites are used in forecasting weather, studying the upper region of the atmosphere, in mapping, etc. If the product of mass of the bodies increase the force of attraction also increases between themand if the square of the distance between the bodies increases, force decreases. By using the above equation he calculated the value of G. Whenthe big spheres are taken to the other side of the ellipse (shown by dotted circles), the bar AB rotates a little since the torque reverses direction. He introduced 2 very big balls and those balls are near the smaller balls. Gravitation | NCERT Class 9 Chapter 11 Notes, Explanation, Question and Answers. = – GMm / 2r. (ii) Law of area The radius vector drawn from the sun to a planet sweeps out equal areas in The value of ‘g’ is taken as positive in the case of object moving towards earth and taken as negative in the case of object is thrown in opposite direction of earth. Academic Partner. Although, of negligible importance in the interactions of elementary particles, gravity is of primary importance in the interactions of objects. The energy required to remove a satellite from its orbit around the earth (planet) to infinity is called binding energy of the satellite. NCERT Solutions for Class 11 Physics. Its S1 unit is N/m and its dimensional formula is [LT-2]. (a) Inertial mass = force / acceleration NCERT solutions Class 11 Physics Chapter 8 Gravitation is a vital resource you must refer to score good marks in the Class 11 examination. centre of mass. Therefore, g is minimum at equator and maximum at poles. Orbital velocity of a satellite is the minimum velocity required to the satellite into a given orbit around earth. There satellites revolve around the earth in polar orbits. CBSE NCERT Notes Class 11 Physics Gravitation. Chapter 8 Gravitation, PDF to download free. 731k watch mins. Class in Hindi and notes in English. (ii) Law of areas. Every object in the universe attracts every other object with a force which is called the force of gravitation. Gravitational force is a attractive force between two masses m1 and m2 separated by a distance Attraction of Earth on Objects close to its Surface When an object is near the surface of earth, the distance between object and centre of the earth will be equal to the radius of earth (i.e. Class 1 - 3; Class 4 - 5; Class 6 - 10; Class 11 - 12; CBSE. BNAT; Classes. Brain Games for Sharper Minds. Kepler’s first law, the law of orbits, states that the orbit of a planet is an ellipse with the sun at one of the foci. Height from earth’s surface = 880 km (ii) The orbital speed of jupiter is less than the orbital speed of earth. CBSE Class 11 Physics Notes : Gravitation. (iii) the strong nuclear force (also called the hadronic force). The angular velocity of the satellite is same in magnitude and direction as that of angular. Height from earth’s surface = 36000 km INSAT 2B and INSAT 2C are geostationary satellites of India. Practice MCQs on Gravitation for Class 11. These equations can be used to calculate the value of velocity, distance, etc by replacing ‘a’ by ‘g’. RE) because the distance of object is negligible in comparison of the radius of earth. Therefore g decreases with depth from earth’s surface. These satellites are used in communication purpose. Gravitation is one of the four classes of interactions found in nature. We have provided Gravitation Class 11 Physics MCQs Questions with Answers to help students understand the concept very well. The speed of planet varies in such a way that the radius, vector drawn from … Orbital velocity = 8 km / s Chapter 7 : System Of Particles And Rotational Motion, Chapter 9 : Mechanical Properties of Solids, Chapter 10 : Mechanical Properties Of Fluids, Chapter 11 : Thermal Properties of Matter, NCERT Solutions for Class 9 Science Maths Hindi English Math, NCERT Solutions for Class 10 Maths Science English Hindi SST, Class 11 Maths Ncert Solutions Biology Chemistry English Physics, Class 12 Maths Ncert Solutions Chemistry Biology Physics pdf, Class 1 Model Test Papers Download in pdf, Class 5 Model Test Papers Download in pdf, Class 6 Model Test Papers Download in pdf, Class 7 Model Test Papers Download in pdf, Class 8 Model Test Papers Download in pdf, Class 9 Model Test Papers Download in pdf, Class 10 Model Test Papers Download in pdf, Class 11 Model Test Papers Download in pdf, Class 12 Model Test Papers Download in pdf. myCBSEguide provides sample papers with solution, test papers for chapter-wise practice, NCERT solutions, NCERT Exemplar solutions, quick revision notes for ready reference, CBSE guess papers and CBSE important … Therefore, .............. (i) Where, g = acceleration due to gravity. r. The value of G is 6.67 X 10-11 Nm2 kg-2 and is same throughout the universe. Users can download CBSE guide quick revision notes from myCBSEguide mobile app and my CBSE guide website. Free PDF Download - Best collection of CBSE topper Notes, Important Questions, Sample papers and NCERT Solutions for CBSE Class 9 Physics Gravitation. Geostationary Satellite:-. Class 11 Physics Gravitation. NCERT Solutions for Class for Class 11 Physics Chapter 8 gives a detailed explanation of the universal law of gravitation and three vital laws proposed by Kepler. (ii) the electromagnetic force Cavendish performed an experiment to calculate the value of G. To calculate the value of G he took a wooden plank and attached two 2 balls on either side of the plank and hung this with a thin thread from the top. When an object moves such that only gravitational force of earth acts on it, it is said to do “Free Fall”. whose angle of inclination with equatorial plane of earth is 90°. To score good marks in NCERT Class 11 Physics exams you need to go through each chapter. That is why I have bought you Physics Notes for Class 11 Pdf all created by the subject experts. Force is ∝to the product of masses of 2 bodies. CBSE Syllabus Class 12 Maths Physics Chemistry ... CBSE Syllabus Class 11 Mathematics biology chemistry ... CBSE Syllabus Class 10 Maths Science Hindi English ... CBSE Syllabus Class 9 Mathematics Science English Hindi ... Revised Syllabus for Class 12 Mathematics. You cannot hear the sound of the explosion on earth. Digital NCERT Books Class 11 Physics pdf are always handy to use when you do not have access to physical copy. Contact us on below numbers. Relation between escape velocity and orbital velocity of the satellite In this class Practice MCQs on Gravitation will be discussed. If the cork is position. Dec 15, 2020 - Gravitation, Chapter Notes, Class 11, Physics (IIT-JEE & AIPMT) Class 11 Notes | EduRev is made by best teachers of Class 11. Note: We have studied three equations of motion. increases by Rω2at equator. It is a vector quantity and its direction is towards the centre of the earth. Gravitational mass Mg is defined by Newton’s law of gravitation. Gravitational potential energy of any object at any point in gravitational field is equal to the work done in bringing it from infinity to that point. NCERT Class 11 Physics Chapter 8 Gravitation Notes are very useful and important because, it is necessary that all questions are answered in an efficient manner. (i) the gravitational force Copyright @ ncerthelp.com A free educational website for CBSE, ICSE and UP board. Learning the important concepts is very important for every student to get better marks in examinations. NCERT Nots For Physics Class 11 Chapter 8 :- GRAVITATION. Time period = 24 h The value of g is taken to be 9.8 m/s2 for all practical purposes. about its own axis, then acceleration due to gravity at a place having latitude λ is given by. Orbital velocity of a satellite is given by. The angle of rotation can be measured experimentally. (iv) when a body is lying in a freely falling lift. Get Gravitation, Physics Chapter Notes, Questions & Answers, Video Lessons, Practice Test and more for CBSE Class 10 at TopperLearning. Every object in the universe attracts every other object with a force which is called the force of gravitation. NCERT Solutions for Class 11 Physics Chapter 8 PDF Download Gravitational potential at any point in gravitational field is equal the work done per unit mass in bringing a very light body from infinity to that point. Become our. The value of acceleration due to gravity on the moon is about. Free classes & tests ... Hindi Physics. These solutions are prepared as per the latest CBSE syllabus 2020-21. 10:00 AM to 7:00 PM IST all days. Cbse Class 11 Physics Revision Notes Chapter 8 Gravitation by byjus.com . by Neepur Garg. Following three points are important regarding the gravitational force. CBSE Class 11 Physics - Gravitation Notes (1). Contact. called geostationary or parking satellite. It is a vector quantity and its direction is towards the centre of gravity of the body. Watch Now. (iii) at the centre of the earth It is gravity that holds the universe together. Similar Classes. The entire NCERT textbook questions have been solved by best teachers for you. Everysingle body in this universe attracts each other with a force which is ∝to the product of their masses and inversely ∝to the square of the distance between them. Gravitation Class 9 Notes introduces the concept of gravity, which is basically a force that attracts a body towards to centre of another physical body that has mass . where M = mass of the earth = 6.0 * 1024 kg and R = radius of the earth = 6.38 * 106 m. Acceleration due to gravity at a height h above the surface of the earth is given by, Factors Affecting Acceleration Due to Gravity. www.ncerthelp.com (Visit for all ncert solutions in text and videos, CBSE syllabus, note and many more) Physics Notes Class 11 CHAPTER 8 GRAVITATION Every object in the universe attracts every other object with a force which is called the force of gravitation. Extramarks offers NCERT solutions for Gravitation of CBSE Class 11. CBSE Class 11. Newton’s view of Gravitation. For more study material for physics click here - class 11 physics chapter 1 physical world notes. These notes are available in easy to learn format. 1. A satellite which appears to be at a fixed position at a definite height to an observer on earth is He also concluded that all objects in this universe attract each other with a force. opened at the surface of the moon then water will boil. external points of spherical bodies the whole mass can be assumed to be concentrated at its Get Revision notes of Class 9th Science Chapter 10 Gravitation to score good marks in your Exams. The value of g is independent of the mass of the object which is falling freely under gravity. (vi) Gravitational pull of the earth is called gravity. It is denoted by U. Gravitational potential energy U = – GMm / r. The negative sign shows that the gravitational potential energy decreases with increase in distance. It is a situation in which the effective weight of the body becomes zero, Weightlessness is achieved. Gravitational potential energy at height h from surface of earth. These are Problem:- Calculate the gravitational force of attraction between 2 lead balls of mass 20kg and 10kg separated by a distance of 10cm? (ii) It is the weakest force in nature. Value of g = 9.8 m / s2… Get NCERT Solutions, Notes, Solutions to Intext Questions, Examples of Chapter 10 Class 9 Gravitation free at Teachoo.In this chapter, we will learnWhat isGravity?What isUniversal Law of GravitationImportantNatural PhenomenaOccurring Due to GravitationWhat isFree Fall?What isAcceleration Due To Grav (iv) A bottle filled with water at 30°C and fitted with a cork is taken to the moon. energy and potential energy is negative. If you have any query regarding NCERT Solutions for Class 11 Physics Chapter 8 Gravitation, drop a comment below and we will get back to you at the earliest. For Study plan details. Gravitation CBSE Class 9 Science Chapter 11 - Complete explanation and Notes of the chapter 'Gravitation'.. Login. This means something which is stationary. These are those satellites which revolve in polar orbits around earth. VIEWS. Every object in the universe attracts every other object with a force which is called the force of gravitation. Education Franchise × Contact Us. IndrajeetSingh Sangtani. (c) They are equal to each other in magnitude. Gravitation is one of the four classes of interactions found in nature. s = ut + ½at 2. v 2 = u 2 + 2as. 8: Gravitation. If earth stapes its rotation about its own axis, then g will remain unchanged at poles but Angular velocity = 2π / 84 = π / 42 rad / min. Gravitation Class 11 Notes Physics Chapter 8 • Kepler’s Laws of Planetary Motion Johannes Kepler formulated three laws which describe planetary motion. motion. (iii) Effect of Altitude The value of g at height h from earth’s surface, (iv) Effect of Depth The value of gat depth h A from earth’s surface. (v) Gravitational force acting between sun and planet provide it centripetal force for orbital According to him there is a force which is exerted by the surface of the earth because of which all the objects are attracted towards the surface of the earth. Gravitational Constant. If velocity of projection u of satellite is greater than the escape velocity ( v > ve), then the satellite will escape away following a hyperbolic path. (i) A missile is launched with a velocity less than the escape velocity. (v) For a satellite orbiting near earth’s surface, (a) Orbital velocity = 8 km / s Gravitation is one of the four classes of interactions found in nature. MCQ Questions for Class 11 Physics with Answers were prepared based on the latest exam pattern. Gravitation Class 11 Ncert Solutions Class 11 Physics Gravitation Ncert Solution In Hindi 7 by youtube.com. Where G = universal Gravitational constant. This document is highly rated by Class 11 students and has been viewed 23045 times. It is denoted by g and its unit is m/s2. He observed that the small balls got attracted to big balls and wooden plank started rotating and as a result the thin thread started twisting. Angular velocity = 2π / 24 = π / 12 rad / h. There satellites revolve around the earth in equatorial orbits. Newtonwas the first scientist who studied the force of gravitation. E = KE + PE Share. Physics Notes For Gravitation Of Class 11 Download PDF. The space in the surrounding of any body in which its gravitational pull can be experienced by other bodies is called gravitational field. Inertial mass of a body remains unaffected by the presence of other bodies near it. PSLV series satellites are polar satellites of India. Value of G = 6.67×10-11 Nm 2 /kg 2 G is called universal gravitational constant. They are as follows: (i) Law of orbits. focus. Complete NCERT Solutions - Gravitation Class 11 Notes | EduRev chapter (including extra questions, long questions, short questions, mcq) can be found on EduRev, you can check out Class 11 lecture & lessons summary in the same course for Class 11 Syllabus. Escape velocity on earth is the minimum velocity with which a body has to be projected vertically upwards from the earth’s surface so that it just crosses the earth’s gravitational field and never returns. Note Newton’s law of gravitation holde goods for object lying at uery large distances and also at very short distances. Natural satellites are those heavenly objects which are not man made and revolve around the earth. The concepts should be clear which will help in faster learning. 0. Time period = 84 min Gravitation is one of the four classes of interactions found in nature. Gravitation – Notes. Free PDF download of Class 11 Physics revision notes & short key-notes for Chapter 8 - Gravitation to score high marks in exams, prepared by expert Physics teachers from latest edition of CBSE(NCERT… (i) during freely falling under gravity Cbse Class 11 Physics 8 Gravitation Full Chapter By Shiksha House by youtube.com. Since work W is obtained, that is, it is negative, the gravitational potential is always negative. Its diameter at poles is approximately 42 km less than its diameter at equator. Our notes of Chapter 10 Gravitation are prepared by Maths experts in an easy to remember format, covering all syllabus of CBSE, KVPY, NTSE, Olympiads, NCERT & other Competitive Exams. (i) Gravitational force is a central as well as conservative force. (iii) A bomb explodes on the moon. ve = √2 vo. (i) If v < vo, then satellite will move on a parabolic path and satellite falls back to earth. NCERT Books. (iii) If vo < V < ve then satellite shall revolve around earth in elliptical orbit. where, M = mass of the planet, R = radius of the planet and h = height of the satellite from planet’s surface. Newtonwas the first scientist who studied the force of gravitation. However, for = 0.00125 rad / s, (vi) Inertial mass and gravitational mass. Class XI Physics. (b) Gravitational mass = weight of body / acceleration due to gravity BOOK FREE CLASS; COMPETITIVE EXAMS. If satellite is revolving near the earth’s surface, then r = (R + h) =- R, Now orbital velocity, vo = √gR Radius of orbit = 42400 km April 22, 2019. in CBSE. This solution is the result of referring to a number of textbooks by experts. or own an. If velocity of projection U is equal the escape velocity (v = ve), then the satellite will escape away following a parabolic path. And we certainly understand the concern that how hard it is to go through all the chapters for revision during exams. The value of g becomes zero at earth’s centre. gravitation forces between two bodies are action-reaction pairs. Study notes & practice Gravitation sample question papers to score high in school board exams. (i) Shape of Earth Acceleration due to gravity g &infi; 1 / R2 Earth is elliptical in shape. Geo means earth and stationary means at rest. A polar orbit is that orbit. (ii) inside a space craft or satellite Check the below NCERT MCQ Questions for Class 11 Physics Chapter 8 Gravitation with Answers Pdf free download. Force is inversely proportional to the square of the distance between the 2 bodies. (i) Unlike the electrostatic force, it is independent of the medium between the particles. This law holds good for all the bodies in the universe. (iii) It is 1036 times smaller than electrostatic force and 10’l8times smaller than nuclear force. (ii) Rotation of Earth about Its Own Axis If ω is the angular velocity of rotation of earth This happened because of force of attraction between the small balls and bigger balls. Its dimensional formula is [L3r-2]. The sum of its kinetic It fails when the distance between the objects is less than 10-9 m i.e., of the order of intermolecular distances. EduRev is like a wikipedia just for education and the NCERT Solutions - Gravitation Class 11 Notes | EduRev images and diagram are … Gravitational Constant: Cavendish experiment, Schematic drawing of Cavendish’s experiment:-. Intensity of gravitational field at a distance r from a body of mass M is given by. velocity of the earth about its own axis. Revision Notes on Gravitation and Projectile Gravitation:-Kepler’s first law (law of elliptical orbit):-A planet moves round the sun in an elliptical orbit with sun situated at one of its foci.Kepler’s second law (law of areal velocities):-A planet moves round the sun in such a way that its areal velocity is constant. (iv) the weak nuclear forces. The uniform acceleration produced in a freely falling object due to the gravitational pull of the earth is known as acceleration due to gravity. A heavenly object which revolves around a planet is called a satellite. It provides you detailed solutions to questions based on escape velocity, acceleration due to gravity and more. Share on Facebook Share on Twitter. where L = angular momentum and m = mass of the planet. Therefore, there is no effect of rotation of earth about its own axis at poles. = 7.92km / h, if v is the speed of a satellite in its orbit and vo is the required orbital velocity to move in the orbit, then. Gravitation class 11 Notes Physics CBSE CBSE guide notes are the comprehensive notes which covers the latest syllabus of CBSE and NCERT. one sixth of that On the earth and on the sun is about 27 times of that on the earth. It means the where, a = semi-major axis of the elliptical orbit. To download Gravitation class 9 Notes, sample paper for class 9 Mathematics, Social Science, Science, English Communicative; do check myCBSEguide app or website. Artificial satellites are those neaven objects which are man made and launched for some purposes revolve around the earth. Gravitational potential, Vg = W / m = – GM / r. Its SI unit is J / kg and it is a scalar quantity. Escape velocity does not depend upon the mass or shape or size of the body as well as the direction of projection of the body. Ch. Gravitational Constant. We hope the NCERT Solutions for Class 11 Physics Chapter 8 Gravitation help you. CBSE Ncert Notes for Class 11 Physics Gravitation. Plank rotates till twisting force becomes equal to the gravitational force between the balls. → If unit of F is in Newton, m is in kg, d is in metre, then unit of G can be calculated as : G = (F×d 2)/Mm, therefor unit will be Nm 2 /kg 2 Relation between Newton’s third law of motion and Newton’s law of gravitation NCERT Book for Class 11 Physics Chapter 8 Gravitation is available for reading or download on this page. Reading Time: 9min read 0. Near the earth surface, time period of the satellite. Binding energy of the satellite of mass m is given by. (iv) The law of gravitational is applicable for all bodies, irrespective of their size, shape and (i) Law of orbit Every planet revolve around the sun in elliptical orbit and sun is at its one Students should free download the NCERT solutions and get better marks in exams. Orbital velocity = 3.1 km/s Mg = Fg / g = W / g = Weight of body / Acceleration due to gravity. This force is Gravitation force. The value of g changes slightly from place to place. These revision notes will not only … Class in Hindi and notes in English. It includes all the topics given in NCERT class 11 Physics text book. Class 11 Physics Chapter 8 Gravitation Complete Notes by youtube.com. The gravitational force acting per unit mass at Earth any point in gravitational field is called intensity of gravitational field at that point. Please send your queries to ncerthelp@gmail.com you can aslo visit our facebook page to get quick help. Class 11 Physics Revision Notes for Chapter 8 - Gravitation - Free PDF Download Free PDF download of Class 11 Physics revision notes & short key-notes for Chapter 8 - Gravitation to score high marks in exams, prepared by expert Physics teachers from latest edition of CBSE(NCERT) books. Answer: m1= 20kg , m2=10kg , r=10cm = 10/100 = 0.1m, Acceleration due to gravity below the surface of earth, Acceleration due to gravity above the surface of earth. 8e981cb 11th Physics Guide Tn State Board Digital … (ii) It is conservative in nature. (iii) It expresses the force between two point masses (of negligible volume). Kepler’s Law of Gravitation To resolve shortcomings of the models propounded by Ptolemy and Copernicus, Kepler propounded three laws on planetary motion. NCERT Solutions. Get the CBSE Class 9 Science notes on chapter 10 ‘Gravitation’ (Part-I) from this article. The earth attracts objects towards it due to gravitational force. (b) Time period = 84 min approximately (c) Angular speed ω = 2π / 84 rad / min Need assistance? v = u + at. Nov 10, 2020 • 1h . Link of our facebook page is given in sidebar. 1800-212-7858 / 9372462318. equal intervals of time, i.e., the areal velocity of the planet around the sun is constant. = GMm / 2r + (- GMm / r) NCERT Class 11 Physics Gravitation - NCERT Solutions prepared for CBSE students by the best teachers in Delhi. Students who are in class 11th or preparing for any exam which is based on Class 11 Physics can refer NCERT Physics Book for their preparation. And maximum at poles reading or download on this page is independent of the medium between the balls law... Earth is called the force of Gravitation the surface of earth planet revolve around the earth faster learning bodies the... Of their size, shape and position 11 download PDF Gravitation - NCERT solutions Class! Proportional to the moon around a planet is called universal gravitational constant: Cavendish experiment Schematic! Mass 20kg and 10kg separated by a distance of object is negligible in comparison of the satellite into given... And more changes slightly from place to place which will help in faster learning for... High in school board exams visit our facebook page to get better marks in examinations ’ l8times smaller electrostatic! Earth and on the moon is about 27 times of that on the mercury no effect rotation. In Delhi through all the topics given in NCERT Class 11 Physics Chapter 8 Gravitation Full Chapter by House. Increases by Rω2at equator the angular velocity of a satellite all practical purposes is affected the! Missile is launched with a force which is falling freely under gravity value of becomes! Fall ” body is affected by the best teachers in Delhi each other a! 6 - 10 ; Class 4 - 5 ; Class 4 - 5 ; 6. Ncert Books Class 11 NCERT solutions Class 11 Physics - Gravitation Notes ( ). Law of Gravitation product of masses of 2 bodies it includes all the chapters for revision during.. Understand the concept very well of CBSE Class 11 Physics revision Notes from mobile! It fails when the distance of 10cm earth surface, time period of the explosion on earth, due! 10 ; Class 6 - gravitation class 11 ncert notes ; Class 4 - 5 ; Class 6 - 10 Class! In nature therefore g decreases with depth from earth ’ s surface textbooks by experts 8! Acceleration produced in a freely falling object due to the satellite is same in magnitude and as! That is, it is a vector quantity and its direction is towards the centre mass... Complete Notes by youtube.com for Physics Class 11 examination the objects is less than diameter! Is approximately 42 km less than 10-9 m i.e., of negligible )! Is obtained, that is, it is a vector quantity and its direction is towards the of! Sun at one of the earth is 90° always handy to use when you do not have access physical. Velocity less than the escape velocity gravitation class 11 ncert notes orbital velocity of a body unaffected... Called intensity of gravitational field is called gravity mapping, etc natural are... However, for external points of spherical bodies the whole mass can be experienced by other bodies near.! All objects in this Class practice MCQs on Gravitation will be discussed the Gravitation forces between two point (. Vi ) gravitational force of gravitation class 11 ncert notes only … Extramarks offers NCERT solutions for Class 11 Physics exams you to. = ut + ½at 2. v 2 = u 2 + 2as when... Will boil document is highly rated by Class 11 - 12 ; CBSE those satellites which revolve in polar around... Water at 30°C and fitted with a velocity less than the orbital speed of jupiter is less than diameter. ) shape of earth taken to be 9.8 m/s2 for all bodies, irrespective of their size, and! Rated by Class 11 Physics Chapter 8: - Gravitation has been viewed 23045 times do “ free ”. - NCERT solutions Class 11 Physics with Answers to help students understand concept... Among the planets, the gravitational potential energy is negative Nm 2 /kg 2 g is independent of object! Object lying at uery large distances and also at very short distances the balls ) because the distance between particles. Planets, the acceleration due to gravity Gravitation Class 11 Physics Chapter 8 Gravitation by byjus.com a force copyright ncerthelp.com...