3. Car 1 was sitting at rest when it was hit from the rear by car 2 of identical mass. Both cars had their breaks on and they skidded together 6 m in the original direction of motion. If the stopping force is ~ 0.7 x (combined weight of the cars), i.e., μ = 0.7, find the approximate speed of car 2 just before the collision took place. [18.14 m/s]​