#### DaveC426913

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In explaining to a curious member on a another forum what [tex]E=mc^2[/tex] means, I finally came to understand it better myself.

The member wanted to know why c is squared. What sense does it make to square a velocity? I stated comparing it to the kinetic energy formula [tex]K=1/2mv^2[/tex] A 1 ton car moving at 40mph has

Einstein's formula is the same conversion, except that c has been substituted for v (since the resultant photons are all moving at c).

It's as simple as that. Take a mass, figure out what velocity it is moving at, square the velocity and you get the amount of energy.

So,

(I suspect it has something to do with the car transferring its energy to another mass a la Newtons Law, so you're only counting half the energy? But I'm not sure.)

D'OH! I just saw the 'Helpful Posts' at the bottom. This exact question has already been answered...

The member wanted to know why c is squared. What sense does it make to square a velocity? I stated comparing it to the kinetic energy formula [tex]K=1/2mv^2[/tex] A 1 ton car moving at 40mph has

**four**times as much energy as a 1 ton car moving at 20mph. That's why you square the velocity to calc the energy.Einstein's formula is the same conversion, except that c has been substituted for v (since the resultant photons are all moving at c).

It's as simple as that. Take a mass, figure out what velocity it is moving at, square the velocity and you get the amount of energy.

So,

*assuming my thoughts are correct*, what happened to the [tex]1/2[/tex]? Einstein's formula doesn't contain it.(I suspect it has something to do with the car transferring its energy to another mass a la Newtons Law, so you're only counting half the energy? But I'm not sure.)

D'OH! I just saw the 'Helpful Posts' at the bottom. This exact question has already been answered...

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