simple question

[hewj11]

this has prob been answered someplace in this forum but didn't search it.

But in E=mc^2 why do you need to have the speed of light in the equation? How come its not just the exchange energy is matter an vice versa?

Thanks

[Mr Skeptic]

It's a conversion factor, just like 1 kilometer * 1000 meters/kilometer = 1000 meters, a formula for turning one measure of distance into another measure of distance.

[toastywombel]

this has prob been answered someplace in this forum but didn't search it.

But in E=mc^2 why do you need to have the speed of light in the equation? How come its not just the exchange energy is matter an vice versa?

Thanks

 

As skeptic said, it is just the conversion of mass (m) into energy (E). Want the conversion for energy (E) to mass? Just solve the equation for mass (m).

 

m=E/c^2

[hewj11]

thanks for the clear up!

[PaulS1950]

I do a little work with kinetic energy in external ballistics of small projectiles and the formula for the energy of a projectile is the same.

E = MV^2

It is just that mass has to be accelerated to the speed of light to convert all its mass to energy (something to do with the velocity required to break apart the atom?).

I just assumed that the speed of light was the probable reaction velocity. so instead of V^2 it is C^2. It is still velocity squared but the velocity is a constant instead of a variable.

Does that make sense to anyone but me?

[Mr Skeptic]

I do a little work with kinetic energy in external ballistics of small projectiles and the formula for the energy of a projectile is the same.

E = MV^2

 

You forgot the 1/2. It's E = (1/2) MV^2 for kinetic energy at non-relativistic speeds.

 

It is just that mass has to be accelerated to the speed of light to convert all its mass to energy (something to do with the velocity required to break apart the atom?).

 

Nothing with mass can be accelerated to the speed of light, because it would require infinite energy to do so. Nothing without mass can travel slower than the speed of light, because otherwise its energy would be zero.

[PaulS1950]

I always forget that 1/2. The spreadsheet converts weight in pounds to mass and does the division in one step:

W / g / 2 where W is weight in pounds and g = acceleration of gravity

 

You are right, of course, and I should have worded it that the reactions within atoms occur at the speed of light.

I understand the principal even if I can't describe it perfectly. A lot of things in my world are OK when they are "close enough".