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Physics · 2025 · 2 marks
CBSE 2025 · Region 5 · Set 2 · Q20
(a) Why is the mass of a nucleus always less than the sum of the masses of its constituents, i.e. free neutrons and free protons? (b) How is Coulomb…
(a)
Why is the mass of a nucleus always less than the sum of the masses of its constituents, i.e. free neutrons and free protons?
(b)
How is Coulomb repulsion between protons in a nucleus overcome? Explain.
Marking-scheme solution
(a)
Because of the binding of the nucleus some energy is released and hence the mass decreases during the formation of the nucleus.
(b)
By the very strong attraction due to nuclear forces.
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CBSE Class 12 Physics past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.