Car 1 hits car 2 and sets car 2 into 180 degree rotation. Both cars are of similar dimensions and about the same weight. What was the speed of car 1 at impact? Assume that car 2 had a speed of 20 mph (29.3 ft/sec) in the opposite direction at impact. I am stuck in using the conservation of linear momentum because the rotation of car number 2 involves a rotation of 180 degrees. The kinetic energy of car 1 is converted into the rotational energy of car 2. Pi rad = 180 degrees. How do I substitute this into omega squared of 1/2 I omega squared?