Answer to Question #263219 in Physics for haze

Question

A truck of mass 4,000 kg at a speed of 10 m/s due east collides head-on with a car of mass 1,200 kg at a speed 20 m/s due west. After the collision two vehicles are stuck together. What is the total momentum of these vehicles together in units of 10⁴ kg m/s? If they go east (west), the momentum is positive (negative). Include the sign to indicate which direction they go after the collision (positive momentum value for east and negative value for west). If your answer is 20000 kg m/s (20x10⁴ kg m/s) , you simply write 20 as your answer. 

Answer 1

By momentum conservation:

$$m_1v_1-m_2v_2=1.6·10^4\text{ kg}·\text{m/s}.$$