Question

Police Report: There were two individuals involved in the accident. No other passengers were present and no other vehicles were involved. There was a truck of mass 1,936 kg traveling Southbound on H and a compact car of mass 1,077 kg travelling Northbound on HWY 26. A bystander claims to have watched the vehicles collide and slide Southbound off the road into a tall grassy ditch. The grass was determined to have a coeficient of friction of 0.6, while the black top had a negligible amount of friction. After the accident, the two vehicles stuck together and slide for some time at a speed of 16.04 m/s, according to the bystander. After interviewing the two drivers, it was clear that neither driver sustained serious or life threatening injuries. The truck driver claims to have been travelling the speed limit, 45 m/s. The car driver claims to have been driving under the speed limit, 25 m/s. Each driver claims there was debris in the road way and they used the other lane to avoid it without checking for another vehicle. Confirmed debris in the roadway; it was a blown off semi-truck tire Begin your analysis by drawing a picture to visualize BEFORE and AFTER the collision. Include any relevant information about the 1. 2. Draw a free body diagram for the Car and the Truck BEFORE and AFTER the collision. Keep in mind that the vehicles stick together implying they are ONE OBJECT post-collision. CAR BEFORE: AFTER: TRUCK BEFORE: f Use the table provided to keep track of all of your data (Do not account for the sliding yet). Determine the initial momentum of each of the vehicles, and the total momentum of the system. YOU MAY CLAIM THAT THE SYSTEM CHANGE IN MOMENTUM IS ZERO. Since you are asked to ignore the cars sliding off the road in this first part. 3. Initial Momentum Final Momentum Change in Momentum TRUCK CAR SYSTEM 60101 Hins You hoten e e oc ri o report if you ignore the sliding and friction 4. Given the information from the report, can you determine if either of the drivers is lying about their speed during the accident? Later in the investigation, the police officer amends his report to state that the car's computer shows a speedometer reading of 36 m/s at the time of accident and the driver of the vehicle lied in their statement. Amend the above table with the updated information. 5. Final Momentum Change in Momentum Initial Momentum TRUCK CAR SYSTEM Does this data make more sense than the previous? Explain why or why not. 6. Draw a free body diagram for the combine vehicles DURING the slide (during the friction part). 7. What direction are the vehicles accelerating during the slide? What is the value of the acceleration? (Hint: Think about before and after the slide. Are the cars moving? If so how fast?) Since there is friction involved, we MAY NOT apply the law of conservation of momentum to the second half of the accident. We were able to apply it to the first half of the accident because we neglected the frictional aspect. Using your free body diagram from above, determine the frictional force applied to the cars during the slide. (Hint: there are mary ways of doing this problem). 8. 9. Determine the necessary impulse to bring the cars to a stop after the accident. What force is causing the cars to stop? Explain. 10. How long did it take for the cars to slide to a complete stop after the accident? 11. Who do you think is at fault for the accident? Explain.

Answer 1

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