Guest erockest3 Posted December 20, 2011 Share Posted December 20, 2011 (edited) Car Crash Web Quest A traffic accident occurred in a 35 km/hr speed limit zone on Millway Street in which a 3000-kg Cadillac Escalade SUV rear-ended a 2000-kg Subaru Outback Wagon that was stopped at a stop sign. Because the entire police investigative division has gone on vacation to Bora Bora to relax, the mayor has contracted my team of experts to determine what happened and what traffic laws were broken. Using the little bit of data we were supplied we were able to find out enough information to figure out if the driver of the 3000-kg Cadillac Escalade SUV was speeding. Using our kinematics equations we used the formula Vf^2 = Vi^2 + 2ad to figure out the velocity of both the Wagon and the SUV. Using the skid marks we were able to determine the distance and we were given acceleration. On top of that we knew the final velocity had to be zero because the cars came to a complete stop. Using what we knew we solved for Vi and found that the SUV’s initial velocity was 2.8 m/s and the wagon’s initial velocity was 12 m/s. Since we found the velocity of both vehicles and the masses were given we were able to use the equation mv = p to calculate the momentum of both immediately following the collision. We found that the momentum of the SUV equaled a total of 8,400 kg*m/s and the wagon equaled 24,000 kg*m/s. Knowing that the momentum before the collision has to be equal to the momentum after the collision we were able to find the momentum of each vehicle immediately before the collision. We added up each cars momentum from after the collision and got a total of 32,400 kg*m/s but, because the wagon was sitting at a stop sign it had no momentum therefore the SUV had a momentum of 32,400 kg*m/s. After finding the momentum of the cars before the collision we used the equation mv = p to calculate the speed/velocity before the cars collided. Using the given mass of 3000kg and the momentum of 32,400 kg*m/s we found the speed/velocity was 10.8 m/s for the SUV. The speed of the wagon had to be 0 because it was sitting still at the stop sign. Using what we know about conversions we were able to convert 10.8 m/s to km/hr finding out that the SUV was going 38.88 km/hr which was three km/hr over the speed limit. Therefore the SUV was indeed speeding. Developed by: Eric, Rashi, and Ryan Edited December 20, 2011 by erockest3 Quote Link to comment Share on other sites More sharing options...

Guest GuitarGirlx3 Posted December 21, 2011 Share Posted December 21, 2011 A car crash occurred in a 35 km/hr speed limit area on Millway Street in which a 3000-kg Cadillac Escalade SUV collided into a 2000-kg Subaru Outback Wagon that was at a stop sign. We needed to determine whether or not the SUV was speeding or not. We gathered an auto expert, collision expert, and investigator to collect the data needed to find out what happened. First, we listed the variables that were given, such as the speed limit, the mass of the vehicles, the accelerations, and the distance that the automobiles skidded. The acceleration of the SUV was -2m/s^{2}, and for the wagon, it was -3m/s^{2}. The distances of the skid marks were 2m for the SUV and 24m for the wagon. Then, we used kinematic equations to solve for the final and initial velocities of both vehicles. The initial velocity for the SUV was 2.83 m/s, and 12m/s for the wagon. We used the formula vf^{2}=vi^{2}+2ad, modified into vf^{2}-2ad=vi^{2} in order to get the initial velocities. The final velocity for both was 0 because they stopped. Next, we needed to determine the momentum of the automobiles, so we created a Momentum Table. [TABLE="align: left"] [TR] [TD]Objects [/TD] [TD]Pb kgm/s [/TD] [TD]Pa kgm/s [/TD] [/TR] [TR] [TD]SUV [/TD] [TD]3000V [/TD] [TD]8490 [/TD] [/TR] [TR] [TD]Wagon [/TD] [TD]0 [/TD] [TD]24000 [/TD] [/TR] [TR] [TD]Total [/TD] [TD]3000V [/TD] [TD]32490 [/TD] [/TR] [/TABLE] According to the Law of Conservation of Momentum, Pb=Pa, therefore 3000V=32490, and we solved for V, getting an answer of 10.83 m/s. So, that data had to be converted into km/hr, which was 38.988 km/hr. The momentum table helped us determine the momentum before and after the two vehicles collided. To get Pa, we used the equation P=mv (momentum, P, = mass times velocity), which was (3000kg) (2.83m/s) =8490 kgm/s. And for the wagon, it was (2000kg) (12m/s) =24000kgm/s. The Pb for the SUV was its mass times the velocity, which we needed to find, and for the wagon it was 0. The speed of the SUV before the collision was 38.988 km/hr and for the wagon, it was 0. Furthermore, the SUV was speeding at 38.988 km/hr, between 3 and 4 km/hr over the speed limit, which was 35 km/hr. Developed by: Lianna, Harley and Ben Quote Link to comment Share on other sites More sharing options...

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