Two 125 kg bumper cars are moving toward each other in opposite directions. car x is moving at 10 m/s and car z at –12 m/s when they collide head–on. if the resulting velocity of car z after the collision is 10 m/s, what is the velocity of car x after the collision?
–12 m/s
–10 m/s
10 m/s
12 m/s

The magnitude of the amount of energy released by burning a fuel source, measured in energy per unit mass, is called its fuel value. note that the fuel value is the negative of the isobaric specific heat of combustion for the fuel. if all the energy obtained from burning 1.23 pounds of butane with a fuel value of 10.85 kcal/g is used to heat 128.0 kg of water at an initial temperature of 18.3 °c, what is the final temperature? note that 1 lb = 453.6 g.