Force

   When we heard Force,  our first thinking about this word is Pull or Push. When you push something you exert a force toward yourself, and when you pull something then you exert force toward yourself. 

              Not only living body,  non-living body also exert force. Such as tension force in a string, if the heavy block is attached to the string and also Normal force perpendicular to the surface if the block placed on any surface. 

The SI Unit is newton 

Force is vector quantity 

We can find resultant force of body if more then one force act on a body by using law of vector addition. 

According to the Newton's Third law of motion "If a body A exerts a force F on another body B, then B exerts a -F force on A"

      "Every action their is always an equal and opposite reaction." 

Their is four categories in which we can place various types of forces
(1) Electromagnetic Force

(2) Gravitational Force

(3) Nuclear 

(4) Weak Force 

        ( click on the type of force to study )

FE Vs FG

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Gravitational Force

Newton's Law Of Gravitation:
     Newton's Law of gravitation states that,"Every particle of matter attracts every other particle of matter with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them."
   
       F ∝ M m
       F ∝  1/r²
            ∴ F ∝ M m/r²
            ∴ F = G M m/r²
    G is a universal gravitational constant

 SI Unit of universal gravitational constant is Nm²/kg².
  And the C. G. S. unit is dynecm²/g²

Value Of G is 6.673×10^-11

And the dimension of G is
       
             

Points to study in Gravitational Force
👉  Acceleration due to gravity (g)

👉 Variation of 'g' due to Altitude, Latitude          and Depth

👉 Study of Satellite
     1) Projection of satellite
     2) Periodic time of satellite
     3) Binding energy and Escape velocity of           satellite.
👉  Kepler's law of motion

👉 Weightlessness.

👉 Uses of satellite.

👉 About Planets

👉 Black Hole

👉  Acceleration due to gravity (g)

       Let M is mass of the earth, R is radius of the earth. Consider an object of mass m situated on the surface of the earth, g  is  the gravitational acceleration due to gravity at the earth's surface. The weight of the object is equal to gravitational Force acting on it. 

On earth surface,

Weight of the object = Gravitational force 

             

        mg = GMm/R²

    

           g = GM /R²

At height h, 

               gh = GM /(R+h)²

       or   gh = g (R/R+h)²

👉 Variation of 'g' due to Altitude, Latitude  and Depth

(1) Variation of g due to Altitude

  

               gh = g [1-2h/R]

(2) Variation of g due to Depth

      

              gd = g [1-d/R]

(3) Variation of g due to Latitude 

   

              g' = g - R⍵²θ²

                                continue reading 

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Electromagnetic force

👉 Charge :
                    Charge is the property associated with matter due to which it produce the experience electrical and magnetic effect. 

           Current(I) = Charge(Q)/Time(t)
▪ charge is derived quantity 
     
             Q = I×t
               


We know about the Gravitational Force, similarly in the Electromagnetic Force we study the Force which is proportional to the product of their charge and inversely proportional to the square of distance between them. 

   

   👉 Coulomb's Law 

                                     F = k q₁q₂ /r²

                         

    Where q₁ & q₂ are the charges on the particle and 'r' is the distance between them and 'k' is the constant. The Force is attractive if the charges are opposites signs and is repulsive if they are same signs. We can write Coulumb's Law

  

      Where k 

                   k = 1/4πε₀

Where  ε = 8.85419 × 10^-12  C²/N-m²

              And the value of 'k'is 

          k = 9.0×10^9 N-m²/C²

👉 Distribution of Charge    

▪  Linear charge distribution  :    

                            Charge per unit lengta

                  λ = Q/ l

▪Surface charge distribution :

                             Charge per unit area

                   σ = Q/A 

▪Volumetric charge distribution :

                        Charge per unit volume 

                   ९ = Q/V

👉 Relationships between λ, σ & ९ 

       σ = dQ/dA 

          = dQ/l.dx

          = dλ/dx

      ∴ ९ = dσ/dx

  

👉 Electric Field :

  

      The space around an electric charge, where it exerts a force on another charge is an 'electric field'. 

   

              E = KQ/r²

   

   

     Where 'F' is the Force experienced by a small positive test charge q₀ due to charge q.  

        It's SI unit is NC^-1.   It is a vector quantity.  We can add charge is their is more charge responsible for electric field. Then, 

           

✦ Electric Potential Energy :

               It is defined as the amount of work done required in carrying an charge slowly either from infinity to a certain point in the electric field or vice-versa 

         U =q₁q₂/r

✦Electric Potential (V) :

          It is defined as the amount of work done required in carrying unit positive charge slowly either from infinity to a certain point in electric field or vive-versa

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