Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is E=mc² What is it used for?

  1. May 3, 2010 #1
    What is E=mc²

    What is it used for?

    Where can i find more information about it?

    it is related to which topic?
  2. jcsd
  3. May 3, 2010 #2


    User Avatar
    Science Advisor

  4. May 3, 2010 #3
    Re: E=mc²

    Thanks I'll read it:)
  5. May 3, 2010 #4
    Re: E=mc²

    Energy= Mass x Speed of Light(squared)
    Where C represents the speed of light 299,792,458 metres per second (commonly abbreviated 2.99792458 x 108 )
  6. May 4, 2010 #5

    Char. Limit

    User Avatar
    Gold Member

    Re: E=mc²

    It's used in nuclear reactions, as per the conversion of mass into energy or vice versa.

    I believe they can use it to find the energy released when two protons and two neutrons bind to form an alpha particle...
  7. May 4, 2010 #6
    Re: E=mc²

    Basically, the equation E=mc² is a statement of mass-energy equivalence. Mass is energy, and energy is mass.

    Here's an example. Let's say you have a helium balloon of volume 12.4L at standard ambient air temperature and pressure. That volume of helium is equivalent to about 0.002kg of gas.

    Now, let's assume (rather unrealistically) that you were able to convert all of the helium in your balloon into energy. How much energy would this be?

    Using E = mc², we substitute our known values (mass in kg and the speed of light, c, in meters / second) to obtain a result:

    E = (0.002kg)(3.00x10^8)² = approx. 180 TJ (terajoules) of energy.

    To help visualize, 1T of TNT yields approx. 4.184GJ of energy. Thus, the helium in your balloon would yield about as much energy as 43kT (kilotonnes) of TNT!

    Perhaps even more interestingly, the same can happen in reverse. Energy can be used to create a mass (m) of matter. However, as we have seen here, a great deal of energy is required to generate even a small amount of matter!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook