Units for formula

[Supreme_Warlord]

Hi,
I am in the process of doing some calculations using Einstein's E=mc^2 forumla. For anyone who knows, please can you tell me the units to use for m and c to get E in J.

Thanks.

[IDMR]

They are not set, in fact it is often useful to assign a value in which c equals 1. But should one take the following values:

M = grams
C = Speed of Light in centimetres per second

Then

E = Ergs

[Graeme Dice]

Hi,
I am in the process of doing some calculations using Einstein's E=mc^2 forumla. For anyone who knows, please can you tell me the units to use for m and c to get E in J.

Thanks.

If you want answers in physics to be in Joules, then the standard usually is to use metres, kilograms, and seconds in your units. In the case of E=mc^2, the mass is in kilograms, and c is in metres per second to give you the result in J.

[IDMR]

I think our friend here can covert units well enough, since 1 joule equals to ten to the power of seven ergs.

[Asst. Asst. Lt. Cmdr. Smi]

With the formula, the energy released by 1 kg of mass converted into pure energy is 9E16J.

[Durandal]

The standard unit for mass in physics is the kilogram (kg). The standard unit for velocity is meters per second (m/s).

Put those units in E = m(c^2), and you get...

E = kg•(m^2)/(s^2)

The Joule is defined as a Newton-meter (W = Fd, E_k = (1/2)mv^2, et cetera). A Newton is kg•(m/s^2) (F = ma). So, multiplying Newton by a meter gives us Joules.