May 29, 2024
Hey, good to be back! Today I’m going to talk about the misconceptions that people have about mass.

Mass – People misunderstand mass as the amount of matter in an object. That’s completely not true. Mass is not a thing, it’s a property, a property that all energies exhibit. The definition of mass you’ll have learned is of ‘ REST MASS ‘, where people neglect ‘rest’ and then the definition becomes wrong, let’s say incomplete.

Let’s start –

A hydrogen atom has lesser mass than the proton and electron combine that make it up. Yes, LESS but how can something weigh less than the parts that make it up? Because of this – E = mc^2 – the most famous equation in the world of physics which was discovered by Albert Einstein in 1905. His paper on this was only three pages long, can you believe it!!

Today we’re going to discuss what E = mc^2 really means –

Let’s take two boxes of same constituents those objects will not have equal masses.
The mass of the object made out of smaller parts is not equal to the sum of the masses of those smaller parts instead the total mass of the composite object depends on:

  1.   How it’s parts are arranged.
  2.   How those parts move within the bigger object.

Confusing right. To make it simpler lets take two identical wind up watches, which are similar, atom to atom except one of them is fully wound up and running but the other one is stopped. According to Einstein and his equation the clock that’s running has more mass than the clock that is not. Why? Because the hand and gears that are moving have kinetic energy also the wound up springs in the watch have potential energy, thermal energy caused due to friction in the moving parts. So m = E/c^2 says that all of those energy manifests itself as extra mass of the watch. how do you get the extra mass, simple, add all the energies and divide it by the square of the speed of light (c^2). As the speed of light is so huge the extra mass is very tiny so in everyday life we think that mass is an indicator of the matter in an object because the extra mass is very small almost 0.0000000000000000001% of the total mass of the watch, but it’s not zero so if we have the right scales and instruments we can measure the actual mass.

Another example – when you switch on a flash light, the mass of the flashlight decreases as light is lost which is a form of energy, which was previously stored as electrochemical energy inside the battery thus manifesting as the flashlights total mass so once that energy escapes you are not weighing that anymore.
There is also a misconception that mass is converted into energy – all the energy comes out as an expense to the energy stored so mass is not converted to energy and neither is  mass a form of energy. we have been weighing is the energies of the particles all the time.
So, coming back to the hydrogen example. How does that work – Because potential energy can be negative, as when electrons and protons are infinitely far apart lets take there potential energy as zero, as the come closer together their potential energy drops like your potential energy decrease as you go towards the center of the earth, so the potential energy of the electron  and proton in an hydrogen atom is negative. the moving electron also has kinetic energy  but the potential energy is negative enough that the sum of the kinetic and potential energy still comes out to be negative so therefore m = E/c^2 also comes out to be negative so hydrogen atom weighs less than the sum of it’s electrons and protons. Bazinga!!!!
Now let’s see how much you have understood (Challenge Question) – 
1) Which mass will be greater –  The mass of two identical boxes side by side on a scale or the mass of the boxes stacked on top of the other on the scale.   
Find out the answer and write it down on the comment section or mail it to me an dirghvshah@gmail.com with a caption ‘mass problem’.  The first 5 peoples’ name will be acknowledged in  my next blog.

And also if you have any doubts please ask it on the comments section below I will answer it. And also you have doubt regarding any other topic then i may write it as my next blog.                         

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