Example

Question:

Given the mass of iron nucleus as 55.85u and \(A=56\), find the nuclear density.

Solution:

\( m_{\rm{Fe}} = 55.85\,\text{u} \), \( \text{u} = 9.27 \times 10^{-26}\,\text{kg} \)
Nuclear density: \[ \text{density} = \frac{\text{mass}}{\text{volume}} = \frac{9.27 \times 10^{-26}}{(4\pi/3)(1.2 \times 10^{-15})^3} \times \frac{1}{56} = 2.29 \times 10^{17}~\text{kg m}^{-3} \] The density of matter in neutron stars is comparable to this value, showing such objects are as compressed as a big nucleus.