Draw a plot showing the variation of potential energy of two nucleons as a function of distance between them. Identify the regions in which the force between the nucleons is (i) attractive, and (ii) repulsive. Justify your answers.

Plot the variation of potential energy of two nucleons as a function of distance \[\] Identification \[1 / 2+1 / 2 \]Identification: Justification: The potential energy is a minimum at a distance \(\displaystyle \mathrm{r}_{0}\). This means that the force is attractive for distance larger than \(\displaystyle \mathrm{r}_{0}\) and repulsive if they are separated by distances less than \(\displaystyle \mathrm{r}_{0}\). Alternatively: \(\displaystyle F=-\frac{d U}{d \mathrm{r}}\). For \(\displaystyle \mathrm{r}<\mathrm{r}_{0}\), slope is negative and therefore F is positive, i.e. repulsive. For \(\displaystyle \mathrm{r}>\mathrm{r}_{0}\), slope is positive and therefore F is negative, i.e. attractive.