Energy Released In Nuclear Fission
A heavy nucleus of mass number 240 with binding energy per nucleon 7.6 MeV splits into two fragments, each having binding energy per nucleon 8.5 MeV. What is the approximate energy released in this single fission event?
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About This Question
- Subject
- physics
- Chapter
- atoms and nuclei
- Topic
- energy released in nuclear fission
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
216 MeV
Energy is released in fission because the fragments are more tightly bound than the parent, so the total binding energy increases and the surplus appears as kinetic energy. The energy released equals the rise in binding energy per nucleon multiplied by the number of nucleons: E=(BE/A)fragments×A−(BE/A)parent×A=(8.5−7.6)×240. Evaluating, E=0.9×240=216 MeV. The value 16 MeV ignores the mass number and merely multiplies the difference by a small factor. The value 432 MeV doubles the result, perhaps by counting each fragment's nucleons twice. The value 0.9 MeV is just the per-nucleon binding-energy increase and forgets to multiply by the 240 nucleons. The liberated energy appears mostly as kinetic energy of the two fragments, which fly apart under their mutual Coulomb repulsion, with smaller contributions carried off by emitted neutrons and gamma radiation. This matches the NCERT explanation of why fission of heavy nuclei releases roughly 200 MeV. A plausibility check confirms the answer is close to the well-known ~200 MeV released per uranium fission, consistent with a mass-240 nucleus splitting near the curve's descending side.
This medium difficulty physics question is from the chapter atoms and nuclei, covering the topic of energy released in nuclear fission. It appeared in the 2025 exam.
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