1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Nuclear reactions

  1. Mar 13, 2008 #1
    calculate the amount of energy released in the fission of a U-235 nucleus.
    Masses of the particles:
    U-235 = 234.9993u

    what i did was i used delta E=mc^2, where m is the mass of n...which is 1.008.. and i get 1.5x10^-10... why is this wrong?/
  2. jcsd
  3. Mar 13, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    The energy given off is the mass difference between the original U and the total of the decay products.

    U235 = 234.9993
    Ba+Kr+n=140.883+91.905+1.008 = 233.796
    difference = 1.203 then just E=mc^2
  4. Mar 13, 2008 #3
  5. Mar 13, 2008 #4
    delta E=1.795x10^-10J....is this answer correct?
  6. Mar 13, 2008 #5
    i got it:)...the answer is 2.82x10^-11J.
  7. Mar 13, 2008 #6


    User Avatar
    Science Advisor
    Homework Helper

    If you did the arithmetic correctly!
    Typical U235 fission is around 200Mev or 3E-11J but depends on the exact breakup products
    with U235->Ba + Kr you would normally get 2 'extra' neutrons so your free energy is only about 0.2u
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Nuclear reactions
  1. Nuclear Reaction (Replies: 2)

  2. Nuclear reaction? (Replies: 6)

  3. Nuclear reactions (Replies: 8)

  4. Nuclear Reaction (Replies: 2)

  5. Nuclear Reactions (Replies: 6)