Read Nuclear Decay: Mass Defect and Q-Value
Decay energy begins with mass difference. Convert the mass defect to energy, then apply momentum conservation when the question asks how products share that energy.
Nuclear Q-Values and Energy Sharing is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Start with the condition
For atomic masses, keep electron bookkeeping consistent. In two-body decay at rest, both products have equal and opposite momentum, so kinetic energies are inversely proportional to mass.
Build the governing relation
A neutrino makes β decay a multi-body process; its Q-value is still set by the total mass difference.
Finish with a physical check
Check the limiting case before selecting an option: remove the special feature in the diagram or make the relevant parameter very large or very small. The result should reduce to a familiar relation.
OlympIQ exam lens
- ✓State the physical condition before choosing a formula.
- ✓Keep direction, sign and constraint information explicit.
- ✓Test one limiting case before committing to an option.
Assigning the full Q-value to one product ignores recoil or the unobserved neutrino.
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