Okay here is my question I have spent 6 hours on it and I can't get the answer. the Question is: a 920kg car is driving down the road and hits a 2300kg SUV stopped at a red light. The two cars lock together and their break lock. they then slide forward 2.8m. A police officer know that the coeficient of friction between rubber and pavement is 0.8. Whith this he can figure out the speed at which the car was going when it hit the SUV. Find the speed of the car just before the collision. I really hope someone can help me.