There are many ways investigator's can use physics to figure out what happened in a crime scene or an accident but one way is by using momentum. By using momentum they can figure out how fast the car was going to determine if that person really stopped at the red light or stop sign. This is possible because if somebody didn't stop at a stop sign and T-boned another car you would be able to figure out that they never stopped because the accident would be greater. The momentum in the car would be greater because the speed was greater therefore more damage would be done to the car that got hit. This is helpful because without it you would have to take the person's word if they said "I stopped at the stop sign". But there's a way to figure it out and therefore the person can be charged accordingly. Momentum is crucial in determing what really happened at a accident because it makes it easy to figure out how fast they were going and what really happened at the scene of the accident.