PHYS130 Accident Reconstruction Lab - STUDENT VERSION-2

docx

School

Siena College *

*We aren’t endorsed by this school

Course

130

Subject

Physics

Date

Apr 3, 2024

Type

docx

Pages

Uploaded by leonardrebecah30

Siena College - General Physics 130 Accident Reconstruction Lab Goals 1. Investigate a real-world physics problem involving 2-D collisions that applies conservation of momentum and work-energy phenomena. 2. Engage with estimations and simplifications in a real-world physics problem. 3. Design your own experimental procedure to solve a real-world physics problem. Experimentation Available equipment: ● Protractor ● Ruler or meter stick ● Additional web resources ● Any other equipment you request that can be provided by your instructor Experimental Procedure Planning In order to create your experimental procedure, discuss the following questions with your team members. Your discussion and responses to these questions will essentially become your team’s agreed upon experimental procedure. You may use this space to create a draft and/or notes of the procedure that you will compose in the lab write-up. 1. What are some quantities that you think would be useful to measure? Distance, velocity, time, force 2. How are you going to measure each quantity? What equipment do you need? Are there any other pieces of equipment that are not on the list above that you could benefit from using to perform your experiment? If so, please list them here and ask your instructor if they are available. A meterstick, a timer/stopwatch 3. What does each team member need to physically do when your experimentation is taking place in order to correctly measure each quantity? 4. How do you think you will know if you performed your experiment well enough? Should you consider running your experiment multiple times? If so, why? 5. Look back at the purpose of this experiment. What will you need to do after you collect your data (obtain the quantities you listed in question 1) in order to accomplish our goals? 1

Siena College - General Physics 130 Accident Reconstruction Lab Name: Date: ______________ Group Members: _ A Day in the Life of Janice Henry, Traffic Cop 1 PART 1 At 13:20 on the last Friday in September, 1989 a frantic call was received at the local police station. There had been a serious automobile accident at the intersection of Main Street and State Street, with injuries involved. Lt. Janice Henry arrived at the scene 10 minutes after the phone call and found that two cars had collided at the intersection. In one car, the driver was unconscious. In the other car, both the driver and the one passenger were injured. After the emergency vehicles transported the injured to the hospital, Lt. Henry's responsibility is to investigate the accident in order to determine whether one of the drivers (or both) are responsible. With the severity of injury in this accident, the investigation is critical. Scientific Ability Missing Inadequate Needs Improvement Adequate D1 Is able to identify the problem to be solved No mention is made of the problem to be solved. An attempt is made to identify the problem to be solved but it is described in a confusing manner. The problem to be solved is described but there are minor omissions or vague details. The problem to be solved is clearly stated. B 3 Is able to decide what parameters are to be measured and identify independent and dependent variables The parameters are irrelevant. Only some of the parameters are relevant. The parameters are relevant. However, independent and dependent variables are not identified. The parameters are relevant and independent and dependent variables are identified. B 6 Is able to identify the shortcomings in an experiment and suggest improvements No attempt is made to identify any shortcomings of the experiment. The shortcomings are described vaguely and no suggestions for improvements are made. Not all aspects of the design are considered in terms of shortcomings or improvements. All major shortcomings of the experiment are identified and reasonable suggestions for improvement are made. 1. What questions does Janice Henry have to answer in this investigation? What measurements does she need to take? What data should she collect? What 2

Siena College - General Physics 130 Accident Reconstruction Lab other information does she need to record in order to aid the investigation? What physics principles will Janice Henry need to use in order to help analyze the data and answer her questions? Officer Henry has to answer how fast each car was going and whether or not car 2 stopped at the stop sign. The data she should collect is the mass of each vehicle and the coefficient of friction between the tires and the road. Janice will need the physics principles of momentum conservation and conservation of energy in order to help analyze the data and answer her questions. 2. If two cars moving at right angles to each other collide, in what direction do you expect the cars to be moving after the collision? The two cars will collide and go in the direction of where they collide. If two cars are moving at right angles when they collide they will move at a 45 degree angle from their initial direction. 3. What factors will influence the direction and distance traveled after impact? The factors that will influence the direction and distance traveled after collision are the masses of the vehicles, the coefficient of friction between the road, the tires and the initial velocities of the cars and the angle of impact of the vehicles. PART 2 Refer to the attached “Field Sketch”. Main street, a thoroughfare, has a 45 mile per hour speed limit. State Street also has a 45 mile per hour limit, but has a stop sign on either side of the road. Vehicle 2, which weighs 5800 lbs, skidded for 24 feet before coming to a stop next to the utility pole, marked Dec #20. Vehicle 1, which weighs 2060 lbs, showed no skid marks after the impact and came to rest next to the house on the corner. Looking at the impact areas of the cars, it was clear to Lt. Henry that the cars impacted at right angles, hitting the front right bumper of vehicle 2 and the front left bumper of vehicle 1. After impact, they initially were traveling in the same direction. Lt. Henry noted that the weather was clear and sunny, 69° and the roadway was dry. Before Janice Henry got any further in her analysis, she was informed that the driver who was unconscious at the scene of the accident was in a coma at the hospital. 3

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Siena College - General Physics 130 Accident Reconstruction Lab Scientific Ability Missing Inadequate Needs Improvement Adequate B9 Is able to devise an explanation for an observed pattern No attempt is made to explain the observed pattern. An explanation is vague, not testable, or contradicts the pattern. An explanation contradicts previous knowledge or the reasoning is flawed. A reasonable explanation is made. It is testable and it explains the observed pattern. 4. Can you make an educated guess about which driver is in a coma based on the evidence so far? Justify your answer. The driver of vehicle 1 is in the coma because vehicle 2 is larger in mass so therefore would apply a larger force onto vehicle 1. Also, car 1 has no skid marks so the driver possibly didn’t hit the brakes 5. Why would Janice Henry note the weather and the condition of the road? The weather and condition of the road can affect the friction and visibility on the roads. 6. Why did vehicle 1 travel further than vehicle 2? Vehicle 1 traveled further than vehicle 2 since vehicle 1 weighs less than vehicle 2 and received a larger impulse from the impact than vehicle 2 did and was most likely traveling at a higher speed carrying more momentum than vehicle 2. n Vehicle 1 traveled further because it has a smaller mass PART 2 (continued) Janice Henry has to determine whether the driver of vehicle 2 ran the stop sign and/or if the driver of vehicle 1 was speeding. Scientific Ability Missing Inadequate Needs Improvement Adequate D2 Is able to design a reliable experiment that solves the problem The experiment does not solve the problem. The experiment attempts to solve the problem but due to the nature of the design the data will not lead to a reliable solution. The experiment attempts to solve the problem but due to the nature of the design there is a moderate chance the data will not lead to a reliable solution. The experiment solves the problem and has a high likelihood of producing data that will lead to a reliable solution. 7. Outline a procedure that Lt. Henry can use to answer these important questions. Be sure that your reasoning is sound, since she will have to testify in court on the evidence. 4

Siena College - General Physics 130 Accident Reconstruction Lab Lt. Henry can use conservation of momentum to determine the vehicles of the velocities before, during and after the impact. This can let us figure out how fast vehicle 1 and vehicle 2 were traveling before the impact. First, we will solve for the speed right before the time of impact using these equations: Then we will solve for their velocities using the coefficient of friction between the cars and the road and the length of the skid marks made by both vehicles prior to impact when they applied their brakes. The kinematics equation vf^2= vi^2+2ad can be utilized to solve for the initial velocity of each vehicle. Vf would equal the speed right before the time of impact for each respective vehicle. D would equal the length of the skid marks made by both vehicles and a would equal the force of friction divided by the the mass of the respective vehicle to find the deceleration. The force of friction is the coefficient of friction between the cars and the road times the mass of the respective vehicle times gravity. From there we can determine the initial velocities of each vehicle and determine if the driver of vehicle 1 was speeding . 5

Siena College - General Physics 130 Accident Reconstruction Lab 8. Does Janice Henry have all the information she needs to determine the velocities? Yes, Janice has all the information she needs to determine the velocities. PART 3 Lt. Henry used a drag sled to determine that the coefficient of friction between the tires and road was 0.60. She can't use the drag sled to determine the coefficient of friction between the tires of vehicle 1 as they roll over the roadway and grass. Scientific Ability Missing Inadequate Needs Improvement Adequate D7 Is able to choose a productive mathematical procedure for solving the experimental problem Mathematical procedure is either missing, or the equations written down are irrelevant to the design. A mathematical procedure is described, but is incorrect or incomplete, due to which the final answer cannot be calculated. Or units are inconsistent. Correct and complete mathematical procedure is described but an error is made in the calculations. All units are consistent. Mathematical procedure is fully consistent with the design. All quantities are calculated correctly with proper units. Final answer is meaningful. 9. Does she need this information? What procedure can she use to find out this information? She does not need this information. To find out this information she can use the distances the car traveled on the grass and the velocity of the car before it left the pavement to find the coefficient of friction of the grass. Using the equation vf^2= vi^2+2ad, we can rearrange the equation to solve for a. a= F/m 10. Using your outlined procedures, find the velocities of the two vehicles just prior to impact and estimate the coefficient of friction between the rolling tires of vehicle 1 and the roadway and grass. Be sure to state any assumptions that you make and justify them. The velocity of car 1 before impact is 25.06 m/s and the velocity of car 2 before impact is 8.90 m/s. 11. During the collision, which vehicle delivered the greater force of impact? Justify your reasoning using physics principles. Vehicle 2 delivered the greater force of impact because it is significantly heavier than vehicle 1 which made vehicle 1 experience a greater acceleration than vehicle 2. The change in momentum of vehicle 1 is also greater than 6

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Siena College - General Physics 130 Accident Reconstruction Lab vehicle 2’s since vehicle 1 was initially traveling at a higher velocity before impact and would have a greater change in velocity compared to vehicle 2. 12. How can Lt. Henry determine the speeds of both vehicles just before they applied their brakes? What further information will she need? She can determine the speeds of both vehicles just before they applied their brakes by using the length of the skid marks made by both vehicles prior to impact. She will also need to use the force of friction between each of the cars and the road respectively to calculate their acceleration when they hit the brakes. PART 4 Lt. Henry measured the skid marks made by both vehicles prior to impact. The skid marks for vehicle 1 were 20 feet in length and the skid marks for vehicle 2 were 7 feet in length. Scientific Ability Missing Inadequate Needs Improvement Adequate D7 Is able to choose a productive mathematical procedure for solving the experimental problem Mathematical procedure is either missing, or the equations written down are irrelevant to the design. A mathematical procedure is described, but is incorrect or incomplete, due to which the final answer cannot be calculated. Or units are inconsistent. Correct and complete mathematical procedure is described but an error is made in the calculations. All units are consistent. Mathematical procedure is fully consistent with the design. All quantities are calculated correctly with proper units. Final answer is meaningful. C8 Is able to make a reasonable judgment about the hypothesis No judgment is made about the hypothesis. A judgment is made but is not consistent with the outcome of the experiment. A judgment is made, which is consistent with the outcome of the experiment, but assumptions are not taken into account. A judgment is made, consistent with the experimental outcome, and assumptions are taken into account. 13. How fast were both cars going just prior to hitting their brakes? Vehicle 1 was traveling at 26.43 m/s prior to hitting their brakes and vehicle 2 was traveling at 10.21 m/s prior to hitting their brakes. 7

Siena College - General Physics 130 Accident Reconstruction Lab 14. Which driver do you recommend Janice Henry cite in the accident? Justify your answer, since Lt. Henry will need to make an airtight case in court. I recommend that Janice cites the driver of vehicle 1 in the accident since vehicle 1 was traveling over 10 mph over the speed limit which gave the driver of vehicle 2 less time to react. FIELD SKETCH 8

Siena College - General Physics 130 Accident Reconstruction Lab ADDITIONAL RESOURCES ● National Highway Traffic Safety Administration o http://www.nhtsa.gov/ ● Custom Design & Consultation: Accident Reconstruction Resources o http://www.c-design.com/accrec.html ● National Association of Investigative Specialists: Links related to accident investigation, highway safety, and accident reconstruction o http://pimall.com/nais/links.acc.html ● Texas Association of Accident Reconstruction Specialists: Hot links to related sites o http://www.taars.org/links ● PBS Nova Online: Escape!: Car Resources o http://www.pbs.org/wgbh/nova/escape/resourcescar.html 9

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

PHYS130 Accident Reconstruction Lab - STUDENT VERSION-2

Related Documents