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PROPORTIONALITY

      The word 'proportional' appears in almost all the physics laws.  Let us have a look at it.



     Look at the above figures.  Here, as the diameter increases, so is the circumference of the circles.

So circumference is proportional  to the diameter.   or
C is proportional 2r 
       hence, there must be some relationship between C and 2r.  Or 2r is scaled to circumference by some number.  That number is called constant of proportionality,

Therefore C= constant* 2r
       or  Constant= C/2r

    By drawing numbers of circles, measuring C and Diameter and dividing one by the other, we can arrive at the constant which happens to be 3.14...=pi

   Finally,C = pi*2r
                 C= 2*pi*r

other examples,
1. force is proportional to the momentum : constant=1
2. current is proportional to the voltage:  constant=R. resistance of the wire.
Also
1. Frequency of the waves is inversely proportional to its wavelength.
Constant:  Velocity of waves.
2. volume of gas is inversely proportional to the pressure
   Constant =1

    Nature loves proportionality.  Our body structure must be proportional.  Banana trees cannot bear coconuts.

     A dot like LED produce powerful tiny light waves.  But, to produce energetic sound waves, heavy speakers are required.