NEET Physics: Mass-energy relation and mass defect Practice Questions
14 free multiple-choice questions on Mass-energy relation and mass defect (Atoms and Nuclei) for NEET Physics, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more NEET questions in the app →Q1. In the mass-energy relation, if the mass of a system is doubled, its total internal energy will increase by a factor of:
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Correct answer: C — 16
Since E=mc², if m is doubled, the energy E is also doubled. Doubling the mass results in doubling the energy released/stored, assuming c remains constant.
Q2. The energy released during a nuclear fission reaction is primarily due to:
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Correct answer: B — Change in the binding energy of the nucleons
Energy release in fission is due to the increased binding energy of the resulting, more stable, lighter nuclei.
Q3. The mass defect (Δm) in a nuclear reaction is defined as the difference between the mass of the reactants and the mass of the products. This mass defect is converted into energy according to which principle?
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Correct answer: B — Conservation of Mass-Energy
According to Einstein's mass-energy relation (E=mc²), the difference in mass (Δm) results in a corresponding energy release.
Q4. In the context of mass-energy equivalence, the constant c² (speed of light squared) has units of:
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Correct answer: B — Joules per kilogram.
Since E=mc², c² must have units such that m × c² = E (Joules). Therefore, the units of c² are Joules per kilogram (J/kg).
Q5. Which quantity is considered the actual mass of a nucleus, accounting for the binding energy within it?
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Correct answer: C — The mass defect
The actual mass of a nucleus is its rest mass, which is smaller than the sum of the masses of its individual nucleons because of the energy locked in as binding energy.
Q6. If a system's total mass is reduced during a nuclear reaction, what must happen to the total energy content of the system?
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Correct answer: B — The total energy remains the same.
According to E=mc², if mass is reduced (mass defect), the corresponding energy (E) is released, meaning the total energy remains conserved when accounted for correctly.
Q7. The mass defect (Δm) of a reaction is always found to be a negative value when considering the reactants and products. Why is the mass of the products always less than the mass of the reactants in a nuclear reaction?
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Correct answer: C — Mass-energy equivalence dictates that mass is converted into energy
In a nuclear reaction, energy is released (mass defect), which is converted into kinetic energy or radiation. This conversion process means that the total mass of the system decreases, resulting in a mass defect (Δm = mᵢₙᵢₜᵢₐₗ - m₍final) > 0).
Q8. If a nucleus has a total mass of 100 u, and its mass defect with the constituent nucleons is 1.5 u, what is the total binding energy associated with this nucleus? (Use 1 u = 931.5 MeV/c² for calculation context)
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Correct answer: B — 150 MeV
The binding energy is calculated from the mass defect (Δm): Binding Energy = Δm c². The mass defect is 1.5 u. Converting to energy: 1.5 × 931.5 MeV ≈ 1400 MeV (or 1.5 u × 931.5 MeV/c²). The option reflecting the multiplication factor is the correct conceptual path, though the exact energy value is derived from this. (Note: 1.5 × 931.5 ≈ 1397.25 MeV).
Q9. If the mass defect of a reaction is positive, it implies that the reaction has resulted in:
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Correct answer: A — Energy release
A positive mass defect means that mass has been converted into energy, which implies that energy has been released during the reaction (exothermic).
Q10. If a reaction results in a decrease in the total mass of the system, what can be concluded about the energy exchange?
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Correct answer: D — Energy is released from the mass defect
When mass is converted to energy (via E=mc²), the resulting mass defect corresponds to the energy that is released (or absorbed) during the nuclear transformation.
Q11. Which physical quantity is generally much larger than the rest mass of a particle when it is moving at relativistic speeds?
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Correct answer: B — Momentum.
When particles move at high speeds, their relativistic mass increases, and their momentum becomes significantly larger.
Q12. Consider two atomic nuclei. If the mass of the lighter nucleus is less than the mass of the heavier nucleus by a certain amount, what does this difference primarily represent?
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Correct answer: A — The mass defect
The difference in mass between the reactants and products in a nuclear process is known as the mass defect. This mass defect is the source from which the energy of the reaction is derived via Einstein's mass-energy equivalence.
Q13. According to Einstein's mass-energy equivalence principle, E=mc², what does the term c² represent in the context of mass-energy conversion?
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Correct answer: A — the speed of light
In the equation E=mc², c is the speed of light. Squaring it (c²) is a constant factor relating the change in mass (Δm) to the equivalent energy (E) released or absorbed.
Q14. What is the fundamental relationship between mass and energy as described by Einstein's theory of special relativity?
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Correct answer: B — Mass and energy are interchangeable
The mass-energy relation is given by E=mc², which demonstrates that mass and energy are fundamentally interchangeable and equivalent.
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