CO$^{-}$ ion moving with kinetic energy of 20 keV dissociates into O$^{-}$ and C which move along the parent ion direction. Assuming no energy is released during dissociation, the kinetic energies of the daughters $(K.E.)_{O^-}$ and $(K.E.)_C$ are related as}
Concept:
Momentum conservation:
\[
p = mv
\]
For same direction breakup, momentum is conserved and kinetic energy depends inversely on mass:
\[
K = \frac{p^2}{2m} \Rightarrow K \propto \frac{1}{m}
\]
Step 1: Masses.
\[
m_O = 16,\quad m_C = 12
\]
Step 2: Energy ratio.
\[
\frac{K_{O^-}}{K_C} = \frac{m_C}{m_O} = \frac{12}{16}
\]