# Mass2Energy

“Splitting the nucleus”

The protons struck a Lithium target placed at and angle of 45 degrees to the beam

* The products of the reaction were emitted at right angles to the proton beam and struck Zinc sulphide screens producing small flashes of light called scintillations which could be seen with a microscope

* It was shown that the products were Helium nuclei (i.e. alpha-particles), emitted in opposite directions with the same speed. How could you find out how much energy is created ?

Where does the energy come from ?

mass of proton = 1.6726 × 10–27 kg;

mass of lithium nucleus = 1.1646 × 10–26 kg;

mass of helium nucleus = 6.6443 × 10–27 kg;

mass of alpha particle = 6.6447 × 10–27 kg

Conservation of energy & mass E = mc2

speed of light = 2.9979 × 108 m s–1,

Planck constant = 6.626 × 10–34 J s;

How do you calculate mass difference and energy in Joules and MeV?

charge on electron = 1.6022 × 10–19 C;

Mass and energy are equivalent and can be interchanged. Einstein’s equation, E = mc2, relates mass and its energy equivalent. Conversion of mass to energy is the source of the energy released in nuclear reactors. 1 atomic mass unit of mass, when anhilitated, provides 931 MeV of energy.

Appropriate calculations.

2012 question 8 honours paper. You need to get the mass of the neutron and it needs to be in AMU according to the scheme. I could not find it in the log tables so I divided the mass of a neutron by the mass of 1 AMU but I got 1.088664096 . In the marking scheme it is 1.008672 .

The law of conservation of momentum holds at the subatomic level too.

The Law states the momentum of all the involved particles before an interaction is equal to their momentum after. This did not seem to hold true. The velocities of the particles were not usually adding up to the speeds predicted by the conservation of momentum. Wolfgang Pauli predicted there were some very small neutral particles that are also emitted. This would account for the differences in momentum. It was very difficult to detect a small and neutral particle. It was named the Neutrino, after Chadwick had stolen its original name, the neutron for the large neutral particle. Use your log tables to calculate the energy liberated as a neutron decays by beta decay as outlined above

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