# Relativistic energy-momentum equation to estimate momentum.

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#1
A nucleus undergoes beta-decay, emitting an electron with kinetic energy 0.5MeV. The nucleus has an atomic mass A=100, and the nuclear radius is R~5.1 fm

Use the relativistic energy-momentum equation to estimate the momentum.
In the attachment I have the correct solution to the question above in green and below this my attempt in red.

Then I have three questions below this in blue.

My questions are:

1. The numbers I have inserted in red do not give the required 0.87 MeV. What have I done wrong?
2. What does T represent in the correct solution?
3. Does m_0 represent the rest mass of and electron?
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#2
Anyone?
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6 years ago
#3
(Original post by little pixie)
Anyone?
Yep problem is that you are mixing and matching natural units where c=1 with SI units where c=3x10^8

If you are working in MeV then c=1.

you should have sqrt(1.011^2 - 0.511^2) for your red line.
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#4
Thanks natninja.

Referring to the original attachment, would you know what the 'T' represents in the equation E = T + (m0 c^2)?

Does m0 represent the rest mass of an electron?
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