[ \frac{1}{2} m_1 u_1^2 + \frac{1}{2} m_2 u_2^2 = \frac{1}{2} m_1 v_1^2 + \frac{1}{2} m_2 v_2^2 ] [ \frac{1}{2} (5.00 , \text{g}) (20.0 , \text{cm/s})^2 + \frac{1}{2} (10.0 , \text{g}) (0 , \text{cm/s})^2 = \frac{1}{2} (5.00 , \text{g}) v_1^2 + \frac{1}{2} (10.0 , \text{g}) v_2^2 ] [ 1000 , \text{g} \cdot \text{cm}^2/\text{s}^2 = 2.5 , \text{g} \cdot v_1^2 + 5.0 , \text{g} \cdot v_2^2 ]