This is a real life situation, no homework associated. I am a mechanical engineer by degree, but have not actively worked in the field for over 20 years. However, I remember enough to be dangerous. I am looking for some high level, back of the envelope analysis. My wife was involved in an auto accident. She will be vehicle A. Vehicle A is heading south at a 4 way stop. Vehicle B is heading east (to the right of A). Vehicle A rolls to stop as 2 vehicles are crossing the intersection going east and west. Vehicle C is heading north, arrives at the intersection after both A and B. A is driving a mini van and B is driving a mid size car. Much discussion and confusion as to whether A or B arrived first, or both at the same time. The result is clear. Vehicle B impacts vehicle A and drives vehicle A into vehicle C. Vehicle A has $8k damage, vehicle B has deployed airbags, vehicle C is totalled. Yes, all from a 4 way stop. Vehicle B impacted vehicle A in an area centered about the rear wheel of vehicle A. Conditions were clear and sunny. Crash occured at 8 am on a Tuesday morning. Based on my memory of simple physics, the acceleration is distance divided by elapsed time squared. The velocity (average) is the distance travelled divided by the elapsed time. Force of impact is mass times acceleration. Since the time elapsed is not known, if I assume vehicles A and B start to enter the intersection at the same time, then the elapsed time between start of entry and crash will be the same for both vehicles. Thus, the relationship of the accelerations and average velocity is basically the ratio of the distance travelled. This is a typical semi-residential roadway in city limits. The lanes are about 14 feet wide. Thus, vehicle A travelled 25 - 28 feet and vehicle B travelled 6 - 8 feet. Question 1: if both cars entered the intersection at the same time, is it reasonable that one vehicle would be able to accelerate 3 - 4 times and achieve an average velocity of 3 - 4 times that of the other vehicle in this distance? Second question: How does the force calculations play into this? It seems that if both vehicles entered the intersection at the same time, from the position of the crash, vehicle A had to achieve higher acceleration than vehicle B. Vehicle A has a higher mass than vehicle B. Thus, it seems if vehicle B has a lower acceleration and lower mass, vehicle B would not have been able to drive vehicle A into vehicle C with the force that occurs. This does not even consider the friction that must be overcome of vehicle A tires with the road. My conclusion is that vehicle A must have entered the intersection first, and vehicle B must have had a higher acceleration at time of impact. Is my analysis and conclusion sound? What elements have I missed? I'm not looking for accident reconstruction or an expert witness, just an idea if my ideas are sound, and possibly a way to present them. Insurance company is placing 50% blame on both vehicles A and B.