What measurements are taken at the scene of the accident that them understand the motion of the car and the reaction of the driver?

kinetic energy and momentum

speed and force measurement

Explanation:

kinetic energy and momentum:

the basic physics principles of motion and relate them to Newton law of motion.

what happened during a car crash is based on collision in physics. When two cars collide, kinetic energy isn’t conserved, but total momentum is. By measuring the masses of the cars and the distance that they slid together, and accounting for drag forces, investigators can find total momentum. If one car was stopped, it is easy to calculate how quickly the other car was traveling. If both cars were in motion, total momentum still gives investigators a starting point.

the Speed, and force calculation

there is need to calculate various determinant variables such as a vehicle’s distance, speed, nature of collision, damage rate at the time of the crash.

When all the data has been gathered, investigators can determine the force of the collision, as well as the speed the cars were traveling before and during the collision. This is crucial in determining if one driver was at fault for ignoring the speed limit or otherwise driving recklessly.

So, for instance, if investigators know how fast the vehicle was initially traveling, and they have a figure for the average human reaction time, they can calculate how far the vehicle traveled while the driver was reacting to the situation. More complicated formulas can help investigators determine the total braking distance and time.

reference from: https://www.claydugas.com/blog/2016/september/how-forensic-evidence-at-crash-and-accident-site/

v=ir = 3x15 =45 v