Physics

Problem

The mass of a

^4\text{He}

nucleus is

4.00260\,\text{u}

. The masses of a proton and a neutron are

1.00728\,\text{u}

and

1.00866\,\text{u}

respectively. Taking

1\,\text{u} = 931\,\text{MeV}\,c^{-2}

, calculate the binding energy per nucleon of

^4\text{He}

(answer in MeV, correct to one decimal place).

Intuitive explanation

The binding energy of a nucleus comes from the mass defect—the difference between the sum of its separated nucleons and the actual nucleus mass. This "missing" mass has been converted to the energy holding the nucleus together via Einstein's $E = mc^2$ . To find binding energy per nucleon, divide the total binding energy by the number of nucleons, giving you a measure of how tightly bound each particle is on average.

Intuitive explanation

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