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/sci/ - Science & Math

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4190826 No.4190826 [Reply] [Original]

Sci, I AM REALLY CONFUSSED!!!!!

we all love this equation:
E = mc^2

However kinetic ENERGY is
E = 1/2mv^2
we chance change that v into a c so kinetic energy is could be written as

E = 1/2mc^2

So how is the half there???

>> No.4190840

Kinetic energy does not equal mass energy.

>> No.4190846

>E = 1/2mv^2
Wrong. It is only a approximation for the kinetic energy of a slow non-rotating particle.

>> No.4190875

That is exactly not the way E=mc^2 is derived. The mass is radiation mass. It's actually derived as m=E/c^2

>> No.4190883

When you hit light speed you get achievement unlocked and you get twice the energy

>> No.4190939

>>4190826
>E = mc^2
Only for energy of a particle at rest
>E = 1/2mv^2
Classical physics thats is a very close approximation as long as the rest energy>>>kinetic energy

Forgot the actual equation for relativistic energy but the equations you have there do not measure the same thing

>> No.4190948
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4190948

You're confusing two different types of energy. Einstein's mc^2 term refers to energy due to rest mass, but kinetic energy is based on momentum, so it's energy due to speed rather than mass.

But really your question foreshadows a larger question which physicists are grappling with as we speak:3