Physics

PHY120 Assignment Case Study – Using Mechanics to Determine the Cause of an Accident

Important: you must read carefully the assignment information on Canvas before attempting to answer these questions. Also, review section 1.3 of the textbook (pp. 25–28) for how to calculate acceleration. Section 1.4b on constant acceleration, will also be helpful.

For all parts, show the equation you used and the values you substituted into the equation, with units with all numbers, in addition to your answer.

1. Calculate the acceleration rate of the Jeep Grand Cherokee in feet/second/second or ft/s2.

Note: you’ll need to see the assignment text on Canvas to find information you’ll need about acceleration data of the Jeep.

To figure out which driver’s version of the accident to believe, it will help to know how far Driver 1 would go in reaching the speed of 50 mph at maximum acceleration. Then we can see if driver 2 would have had enough distance to come to a stop after passing this point. Follow the next steps to determine this.

2. Calculate how much time Driver 1 would take to reach 50 mph (73.3 ft/s) while accelerating at the rate determined in part 1. Remember that the acceleration rate represents how much the speed increases each second.

See page 32 of the text for information on how to do this.

3. Next we need to figure out how far the car would travel while accelerating at this rate (part 1) for this amount of time (part 2). You have the data you need. Find the right equation and solve. If you get stuck, ask for help before the assignment is overdue.

See page 33 for an example of how to do this.

4. Now it’s time to evaluate the two driver's stories. If driver 2 passed driver 1 after driver 1 accelerated to 50 mph (73.3 ft/s), he would have to have started his deceleration farther down the road from the intersection than the distance calculated in part 3. Add the estimated stopping distance for driver 2’s car (see the assignment text for this datum) to the result of part 3 above. What is this distance?

5. Which driver’s account do you believe and why?

Remember to save your document with your answer before uploading. Make sure you upload to the correct assignment and do so before the due date.

Double check that all your answers are reasonable and have correct units. If you are asked to calculate an amount of time, the units should be in seconds, for example. If you are stuck on how to complete any part of this assignment, ask for help after reviewing the sections of the text referred to above.