# Car Crash WebQuest Challenge ## Recommended Posts Car Crash Web Quest Challenge

Dear Mayor,

I am writing to inform you of a traffic accident concerning a 3000 kg SUV and a 2000 kg Subaru Outback Wagon. The accident occurred in a 35 km/hr speed limit zone where the Wagon was stopped at a stop sign. From our data, we can conclude that the SUV was speeding when the driver rear ended the Subaru wagon. We were able to come to this conclusion from our use of kinematics, the momentum of each car, and the law of the Conservation of Momentum.

The first step we had to take to figure out if the SUV was speeding or not was to find each car’s velocity immediately after the two cars collided. The sketch we were provided with provided us the distance each car traveled after they collided. We were also given the acceleration of each car when they have their brakes locked, and we knew that their final velocity was 0 m/s because they came to a complete stop after the collision. We then used all these factors in order to find the initial velocity of each car, which in this case was each car’s speed after they collided. We used the equation Vf^2=Vi^2+2ad, or final velocity squared equals initial velocity squared plus 2 times acceleration times distance. By using this equation, we found that the SUV was going 2.83 m/s after the cars hit, and the Wagon was going 12 m/s after it was rear ended. From here, we found the total momentum of each car. Since momentum equals mass times velocity, we multiplied each cars velocity after they collided by their masses. We found that the SUV had 8490 kilogram meters per second, while the Subaru had 24000 kilogram meters per second. We then had to add the two totals to find the total momentum of the two cars, which turned out to be 32490 kilogram meters per second. Due to the law of the Conservation of Momentum, we knew that the total momentum after the collision had to be the same of the momentum before the collision. Since the Subaru was stopped, its momentum was zero, which means the SUV carried all of the momentum by itself. We then divided by its mass, 3000 kg, to find that it was going 10.83 m/s before the collision. After some unit conversions, we found that the SUV was going 38.988 km/hr, well over the speed limit.

From our investigation we concluded that the SUV was speeding and it should get a speeding ticket as well as pay for the damages for the station wagon because the station wagon made a routine stop at a stop sign and the SUV wasn’t paying attention and ran into him. Using physics helped us determine the speed of the two vehicles before and after the collision as well as the momentum of both of the vehicles before and after the collision.

Developed by THE peter, lizzie, robert

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