* 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
E=mc2
* 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.
* Einstein:
Instead of k=(0.5)mv2
We must use
K=(m-m0)c2
Or K = mc2-m0c2
As K = E-m0c2
E=m0c2+K
Where E = total energy.
* What does E=mc2 mean?
* It means that mass is a form of energy.
Curve of Binding Energy Gamowtal Deutsches Museum
Curve of Binding Energy Gamowtal Deutsches Museum
The Experimental Apparatus with which the team of ...* 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.
Key Idea:
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...