Question about "m" in E=mc2?

Question

Not that I intend to convert significant amounts mass into energy any time soon, but I would like to know what unit of mass you need to use in the equation should you wish to calculate something. What unit of mass do you multiply with the speed of light and then square to get E?

Obviously, I can convert any unit of mass into kilograms and derive an amount for E once I know how it works using SI. I'm asking what description of mass can you use that does not require a conversion to derive a number for E, as opposed to an equation for an answer. If anybody wants to disagree with stellarfirefly, or the others who answered kilograms, you'll need to explain what definition of force is derived if you use something other than kilograms. Otherwise, stellar gets the blue ribbon for being first.

Answer 1

IIRC, energy in joules equals mass in kilograms times the speed of light in meters per second squared.

Answer 2

You are asking about the difference between dimension and unit. They are NOT the same thing.

Dimension is a fundamental physical quantity like length [L], mass [M], or time [T] but it is not a system for measuring those quantities.

Unit is a system for measuring dimension. The SI unit system uses the unit of kilogram for mass, meter for length, and second for time. The english unit system uses the unit of pound-mass for mass, foot for length, and second for time.. although it has unit-conversion issues.

In any consistent unit system if you multiply a unit of mass by the speed of light (and the appropriate conversion factors) you will get the energy. By conversion factors Im saying that to convert pound-mass * acceleration into force you must divide by gc, because the english units were some of the first made, and they werent made well.. so they were remade as SI, but the US has so much inertia that it cant change to the better system, but the rest of the world.. because it has had to retool after WWII was able to change.

In SI
energy (j) = mass (kg) * speed of light (m/s) * speed of light (m/s)

Answer 3

You must use the Kilogram. In case you were wondering you need to use meters for the speed of light (3*10^8), and the Energy will be in Joules.

Answer 4

Mass in kilograms. Speed of light in meters/second, which becomes meters^2/second^2 after you square it. Energy in Joules.

Answer 5

It depends on the units of energy and speed you use.

However, the standard in modern science is J for energy and m/s for speed. In that case, you must also use the standard unit (kg) for mass because

1 J = 1 kg . (1 m/s)^2

If you have the energy in eV, it is best to convert it to Joules first (multiply by 1.6.10^-19).

Answer 6

You can use any unit of mass, so long as your answer includes the unit of mass your using.

So when you get a value, it should be like j/(unit of mass).

Answer 7

Everyone in physics calculates it in units of electron volts (eV).
It is the amount of energy one electron gains when traversing a
one volt field.

In these energy units, then, the mass is expressed in units of
electron volts per speed of light squared.

For example, an electron will always be written with rest energy
0.511 MeV (Million electron Volts) so its mass is written
0.511 MeV/c^2
where for example,
1 MeV/c² = 1.783×10−30 kg

Answer 8

The first answer is correct, but you could do the calculation using any units you want as long as they are all from the same system

Answer 9

Yes m is in kilograms if E is in joules and c is in metres per second.

Always use SI units.

Answer 10

the amount of mass that is being accelerated