1. The problem statement, all variables and given/known data A 1200kg car travelling initially with a speed of 25m/s in an easterly direction crashes into the rear end of a 9000kg truck moving in the same direction at 20m/s. The velocity of the car right after the collision is 18m/s to the east. 3.4.1) What is the velocity of the truck after the collision 3.4.2) How much of mechanical energy is lost during the collision 2. Relevant equations p=mv ek=1/2mv^2 3. The attempt at a solution The velocity of the truck was worked out to be 21m/s. My problem is with the second question, this is an elastic collision right ?, so their should be no mechanical energy lost ?