PHYS 2010 Written HW 5 Name: Sophie
Brous ID: __________________
1) Breaking a bond
A diatomic molecule’s potential energy, PE, is measured as a function of
the separation, 𝑥, of the two atoms. Note the scale of the axes (nm stands
for nanometers, and eV stands for “electron volt” and the unit conversion
is 1 eV = 1.6 × 10−19 J). Note: for very small values of 𝑥, the potential
energy becomes effectively infinite (off the graph’s positive scale); while
for very large values of 𝑥 the potential energy approaches zero.
A) If the separation between the two atoms at some moment is 0.25 nm,
approximately how much potential energy does the molecule have at
that moment?
B) Total energy is kinetic energy plus potential energy. If the separation is
0.25 nm at some moment, which of the following are impossible values
of total energy for this two-atom system? [Note: in some cases, the
kinetic energy might be enough that the bond will break!]
−4 eV, −2 eV, 0 eV, +2 eV
Circle the values that are impossible. Explain your reasoning.
