A1200-kg car traveling initially with a speed of 25.0 m/s in an easterly direction crashes into the rear end of a 9,000-kg truck moving in the same direction at 20.0 m/s. the velocity of the car right after the collision is 18.0 m/s to the east. a. what is the velocity of the truck right after the collision? b. how much mechanical energy is lost in the collision? account for this loss in energy.