The kinetic energy is given by:
\[ KE = \frac{P^2}{2m}, \quad \text{where } P \propto \sqrt{m}. \]
For masses \(m_A = 400 \, \text{g}, \, m_B = 1.2 \, \text{kg}, \, m_C = 1.6 \, \text{kg}\):
\[ P_A : P_B : P_C = \sqrt{400} : \sqrt{1200} : \sqrt{1600}. \]
Simplify:
\[ P_A : P_B : P_C = 1 : \sqrt{3} : 2. \]
Final Answer: 1 : \(\sqrt{3}\) : 2.