Skip to main content

Gravitation


Gravitation

Gravity is an attracting force, Gravitational force is always attractive in nature and is one of the weakest force. In this chapter,we will be studying about the gravitational force in detail.



    Newton's universal law of gravitation.

    • Do you know that every object in the universe attracts other object!!! and when there is a attraction there must be a force which is being used to help objects attract each other. 
    • According to Newton's law of gravitation, every object in the universe attracts every other object with a force which is directly proportionate to the product of the masses of the objects and inversely proportionate to the square of the distance between the centres of the 2 objects.
    • By this law, we derive the following formula:- 
    • F=GMm/r2 (G is the universal gravitational constant and its value is the same in the whole universe, M and m are the masses and r is the distance between the centres of the 2 object)


    Do You Know ?

    • Gravitational force is the weakest force in nature. 
    • 'G' is the Universal gravitation constant i.e. its value remains the same in the whole universe and its value is G=6.67x10-11 Nm2/kg2

    Importance of gravitational force

    Gravitational force is a very important force and has many importance. 
    • The force of attraction that binds us to the earth.  
    • The motion of planets moving around the sun.
    • The motion of moon around the earth.                    
    • The occurring of tides due to sun and moon.

    Acceleration due to gravity Value of 'g'

    It is the acceleration which a body experiences, when it falls towards the earth due to earth’s gravitational pull. It is denoted by 'g'. Its value is different at every place on earth. we usually take its value as 9.8 m/s2.

    Do You Know ?

    • 'g' does not depend on the mass of the object.
    • According to Newton’s Second law :- F= ma i.e. force = mass*acceleration
    • The value of 'g' on moon is 1/6 the value of 'g' on Earth. As a result a object weighs 6 times more on earth.
    • Value of `g’ is different on different planets, so weight will also be different.
    • Weight of a body decreases with height and also with depth from the surface of the earth.

    Value of 'g'

    According to Newton’s Second law :- F= ma and for a object falling freely towards the earth it  becomes F = mg:-
    Explanation: force = mass*acceleration and when an object freely fall towards the earth it experiences acceleration of 9.8 m/s2  ='g'

    Newton’s Gravitation law  F = GMm/r2 
    When we comparing mg=GMm/r2 (m gets cancelled on both sides) and we get g = GM/R2 (M= mass of the earth)

    Difference between ‘g’ & ‘G’

                           ‘g’
                            ‘G’
    It is the acceleration which a body experiences when it falls towards the earth due to earth’s gravitational pull.
    It is a universal gravitational constant.
    Its value is different at different points on the earth.
    Its value remains same everywhere, as it is a constant
    It is a vector quantity.
    It is a scalar quantity.
    The value of 'g' on the surface of earth is 9.8 m/s2
    The value of G=6.673 x 10-11 Nm2/kg2   .
    Its value can be zero—at the centre of the earth or in space.
    Its value can never be zero.


    Variation in the value of 'g'

    The value of 'g' is not constant and changes due to these factors:

    • The earth is not spherical in shape but it is oval in shape due to which the value of 'g' is more at poles.
    • Value of g decreases with the altitude above the surface of the earth .
    • Value of g decreases as we go deep into earth.      


    Do You Know ?

    There are 3 equations of motion:-
    • v = u + a t                     
    • s = u t + 1/2at2                  
    • v2 –u2 =2as

    Equations of motion for a freely falling body

    The equations of motions can be applied on an object which is freely falling towards earth. These are:-
    • v = u + g t                     
    • h = u t + 1/2gt2                  
    • v2 –u2 =2gh

    Replacing 'a' by 'g' and 's' by 'h' 
    Some important points:-

    1. For a freely falling body, u=0 at the maximum height.
    2. When a body is thrown up, its v=0 at the maximum height.
    3. If a body thrown up, g= - 9.8m/s2.
    4. If a body thrown down, g = 9.8m/s2.

    Difference between mass & weight

                       MASS
                            WEIGHT
    It is the quantity of matter in an object.
    It is the force by which an object is attracted by the earth.
    Its value remains same everywhere, as it is a constant.
    Depends on mass & 'g'.(W=mg)
    It is a scalar quantity.
    It is a vector quantity.
    SI unit is kilogram.
    SI unit is Newton.
    Mass is measured by a beam balance.
    Weight is measured by a spring balance.
    Mass can never be zero.
    Weight can be zero at places like centre of the earth or in space where the value of 'g' is 0





    Recommended For You

    Labels:

    Comments

    Post a Comment

    Popular Posts

    Cathode Ray Experiment

    This experiment was conducted by J.J. Thomson (Sir Joseph John Thomson) in the year 1897. This experiment proved that atom is made up of fundamental particles which are much smaller than the smallest atom 'hydrogen' This experiment helped to discover electron. According to J.J. Thomson, the cathode rays consisted of very light, small and negatively charged particles. He named the particles "corpuscles" which were later known as electrons
    13 comments
    Read more

    Anode Ray Experiment

    →Anode ray experiment was conducted by E Goldstein. →These rays are also known as canal rays. →This experiment helped in the discovery of the proton. Apparatus Used A discharge tube  was taken in which there were 2 electrodes i.e. Anode(+ve) and the cathode (-ve). The tube was filled with an inert gas. A perforated or porous cathode was used. A layer of zinc sulphide was placed at the back of the cathode. There was a vacuum pump in the tube. High voltage (5000v-10000v) was allowed to flow through the system. It was observed that when the gas was at 1atm(atmospheric pressure ) no change was seen in the tube.  When the   pressure   was decreased inside the tube, a glow could be seen at the back side of the cathode.
    3 comments
    Read more

    Rutherford Alpha Ray Scattering Experiment

    Rutherford Alpha Ray Scattering Experiment Hey, Guys, most of you might have heard about the alpha ray scattering experiment and if you want to know in detail about Rutherford's model and the experiment he conducted, this is the right place for you... But first: Things You Must Know Some basic information that will help you understand rutherford experiment properly: Proton is a sub-atomic particle which is positively charged and has a mass of 1u. Alpha particles are helium atom with a charge of +2 as they have lost 2 electrons. Alpha particles have an atomic mass  of 4u. Gold is highly malleable and can be beaten into very thin sheets. Experiment Rutherford conducted his experiment in the following way: Rutherford took a very thin gold foil and bombarded it with high energy alpha particles. He placed a layer of zinc sulphide on the walls where the experiment was taking place because when alpha particles strike zinc sulphide layer, it results i
    37 comments
    Read more

    Important Mathematical Constants!

    Important Mathematical Constants Mathematical constants are those numbers that are special and interesting because they come up in the various fields of mathematics like geometry, calculus etc. These mathematical constants are usually named after the person who discovered it and they are represented by a symbol that is usually picked up from the Greek alphabet. Mathematical constants are by definition very important. In this article we will take a look at certain mathematical constants that are more commonplace than others. 1.       π (pi) or Archimedes constant (~3.14159):   π is defined as the ratio of the circumference of a circle to its diameter. This is probably the most popular mathematical constant. So π is the circumference of the circle whose diameter is 1 unit. You might have seen it popping up when calculating the area of a circle (πr 2 ) or the circumference of a circle (2πr). It has many uses throughout mathematics from calculating the area of certain shap
    6 comments
    Read more

    Paid Apps For Free ??

    Everyone wants to play a game like GTA on iPad, it is easy on a computer to download such games but difficult on smart devices like iPad, tablet,  or smartphones. We can buy them but not everyone can buy games. But no worries guys there is a solution to this problem where one can have fun of playing games without spending their precious money .(underlined apps have downloading links  given at the end) iOS There many apps through which you can download these paid games for free. Also, there are many sites for the same. One of the most helpful apps is a Chinese app.It is called haimawan. If on a ios device, then you just have to click install which will redirect to settings  add a profile  and boom enjoy it as you wish . but it does not always work, it might work for few days and then the verification problem which may not cure. One more app is tutu which is a fantastic app and always work (99.9% sure .. nothing is perfect). X cross was the perfect app but is closed now an
    23 comments
    Read more

    2-D & 3-D GEOMETRY

    2-D & 3-D GEOMETRY We all have some amount of geometry. We know that any line can be represented on the Cartesian plane. Any figure can be drawn on it. But can we represent a 3-d object on it. Yes we can. A Cartesian plane has 2 axis. While representing in 3-D we need to add a third axis. This axis does not come in between the axis or in the same plane. It appears to be coming out of the paper as we cannot represent a 3-d object on a 2-d surface. This new z-axis represents a line coming out of the screen. Before understanding 3-d geometry you need to imagine this axis coming out of the screen.  REMEMBER : all the three axis are perpendicular .i.e there an angle 0f 90 between them and they meet at the origin If you are unable to imagine you can take a thick book as an example. Any corner becomes it origin and the three edges as the three axis REPRESENTING 3-D GEOMETRY Like in 2-d geometry we represent the value of the different axis as (x,y) we use the same m
    3 comments
    Read more

    Animal and Plant Cells

     Cells Cells are the basic functional, biological and structural unit of life. The word cell is a Latin word meaning ‘small room’. Cells are also known as building blocks of life.  The branch of science that deals with the form, structure, and composition of a cell is known as Cytology. All organisms around us are made up of cells. Bacteria, ameba, paramecium, algae, fungi, plants and animals are made up of cells.  Cells together form tissues. And tissue together makes an organ. History Of Cell The cell was discovered by Robert Hooke in 1665. He assembled a simple microscope and observed a very thin slice of cork under his primitive microscope. The cork was obtained from the outer covering of a tree called bark. Robert Hooke observed many little-partitioned boxes or compartments in the cork slice. These boxes appeared like a honey-comb. He termed these boxes as the cell. He also noticed that one box was separated from another by a wall. What Ho
    23 comments
    Read more