* In the 1930's nuclear energy became a serious possibility.
* 1932 - Discovery of the neutron.
* No change, ergo, can probe nucleus.
* Hahn and Strassmann fired neutrons at U nucleus.
* Lise Meitner and Otto Frisch interpreted this:
Neutrons caused splitting of U into smaller nuclei
* Fission had occurred.
* Potent source of energy!
* Energy from
* In more complete form, Einstein showed that at relativistic speeds we cannot use k=(0.5)mv2 .
* Remember from special relativity, that as speed increases, mass increases!
* ie. Work is done on a body: K increases.
* Or Work is done on a body: mass increases.
* Then ENERGY transforms into Mass.
Instead of k=(0.5)mv2
We must use
Or K = mc2-m0c2
As K = E-m0c2
Where E = total energy.
* What does E=mc2 mean?
* It means that mass is a form of energy.
* In principle, we could transform mass into other forms of energy.
* Eg. Convert 1 kg of mass into heat
E=(1)(3.0x 108)2 = 9.0x1016 J.
* Consider a fission reaction:
10n + 23592U = 14038Xc + 9438Sr + 210n
* The mass of products is less than the mass of the reactants!
ie. 23592U 235.0439 u 14038Xc 139.9054 u
n 1.008 u 9438Sr 93.9063 u
210n 2.016 u
236.0519 u 235.8277 u
Difference = 0.2242u ( or about 0.0095%)
The difference is small, but the c2 term means the energy will be large.
This introduces an idea called BINDING ENERGY, which we will consider.
When individual; nucleons are brought together to from nuclei; the mass of the nucleus is less than that of the sun of the sum of the masses of the individual nucleons when they are widely separated. Energy is therefore decreased.