Ex: Nuclear Power (Fission) Big nucleus 2 smaller nuclei (less total mass, less energy)

(less total mass, less energy) Ex: The Sun (Fusion) Two small nuclei Larger nucleus (less total mass, less energy)

The sun loses over 4 billion kg per second due to fusion (Don’t worry, it will last for another 5 billion years or so) Inverse square law with light demo Application fusion mass on sun: Establish inverse square law with vernier light kit Draw the comparison with light source as the sun and sensor being a planet ie Earth Research solar constant at earth surface (w/m2) Math! calculate suns total radiant power output: area of a sphere radius of earths orbit around the sun radius of earths 5. Differentiate E=mc2 with respect to time… http://www.itacanet.org/the-sun-as-a-source-of-energy/part-2-solar-energy-reaching-the-earths-surface/

Fusion The joining of two smaller nuclei to form a larger one. This is the process that powers the sun Example of a fusion reaction: When smaller nuclei combine to form a larger one, mass is lost in the form of an energy release. WHY? Fusing two smaller nuclei together results in a nucleus with a higher binding energy per nucleon (see curve) and less energy stored as mass compared to the smaller nuclei. This difference in mass between the smaller and larger nuclei results in a release of energy. Fusion requires extreme temperature (eg millions of degrees) to occur, and has not practically and economically been used in power generation (yet...) The high temperatures are needed to provide the energy for the nuclei to collide and overcome the net repulsion between the two positive nuclei.

http://www. telegraph. co http://www.telegraph.co.uk/news/science/science-news/10679744/British-schoolboy-13-becomes-youngest-to-build-nuclear-fusion-reactor.html

Fusion Summary… Mass-Energy is conserved. Small nuclei have some of their mass-energy as binding energy. The rest of their mass-energy is in the nucleons, as mass.   If two smaller nuclei fuse into a nucleus that has more binding energy per nucleon, the nucleons of the new nucleus have less mass-energy in them. The difference in mass-energy between the reactants and the product is given off as energy, usually as Ek of the products and/or radiation. Need high temperatures so that particles have high kinetic energies to overcome repulsive electrostatic forces in order to fuse.

Which of the following processes releases energy? 35Cl 56Fe 116Sn 194Pt 238U 1 2 3 4 5 6 7

The final step of hydrogen “burning” in stars consists of combining two 3He2 nuclei to form a stable 4He2 nucleus plus two protons. How much energy is released in this final step? The mass energy of the 3He2 nucleus (without atomic electrons) is 2809.41 MeV, the mass energy of the 4He2 nucleus (without electrons) is 3728.40 MeV and the mass energy of a proton is 938.27 MeV. 1.3 MeV 13.9 MeV 130 MeV No energy is released

For the above reaction, assume that each of the deuterium nuclei have the same kinetic energy. What is the approximate kinetic energy they require to overcome coulomb repulsion? The radius of the helium nucleus is 1.55 x 10-15 m and the coulomb potential energy for two proton charges is: 0 MeV 0.10 MeV 0.93 MeV 9.30 MeV 0.46 MeV