A2,511 kg railroad car moving at 4.192 m/s to the east collides with a 8,199 kg railroad car moving at 3.781 m/s to the west. if the cars couple together, what is their velocity after the collision?

The flame produced by the burner of a gas (propane) grill is a pale blue color when enough air mixes with the propane (c3h8) to burn it completely. for every gram of propane that flows through the burner, what volume of air is needed to burn it completely? assume that the temperature of the burner is 195.0°c, the pressure is 1.05 atm, and the mole fraction of o2 in air is 0.210.