Question

Two body of mass 10kg and 4kg are moving at opposite direction with the same velocity of 5m/s. If they collide together after their collision, calculate their common velocity

Answer 1

$$m_1v_1-m_2v_2=(m_1+m_2)v_c,$$ $$v_c=\dfrac{m_1v_1-m_2v_2}{m_1+m_2}=\dfrac{10\ kg\cdot5\ \dfrac{m}{s}-4\ kg\cdot5\ \dfrac{m}{s}}{10\ kg+4\ kg}=2.14\ \dfrac{m}{s}.$$