First, if you have not returned your Quiz 1 revisions, including the original quiz as well as any additional corrections you would like to make, please do so as soon as you can. Some of you did not get Quiz 1 back until Wednesday, so I’m happy to give you a few days extra to complete revisions. But I would like all of them in by Monday, Oct. 16.
Below is a “clean” copy of Quiz 2:
You may choose to correct any part of any question on your original quiz (or on a clean copy) and turn that back in with your revision. In addition, you will be expected to turn in a revised solution to what amounts to question 2d from the quiz (whether or not the original answer was correct). The revision is not a correction (though it can also be a correction!) but an opportunity to work on technical communication skills and deepen your understanding of the concepts, as outlined in my post on the revision assignment.
It may be helpful for your revision to approach your work as if 2d were simply the following homework problem:
A sprinter runs a 100 meter race. Starting from rest, their acceleration is 4.5 m/s2 for the first 2.5 seconds of the race, after which they run at a constant velocity the rest of the race. What will be the sprinter’s total time for the race?
What you should notice about the quiz is that parts a-c were an effort on my part to guide you to a solution. In part a I invited you to consider what kind of motion this problem represents. It is not constant acceleration throughout (I gave an nonzero acceleration for the first 2.5 seconds; but what is the value of acceleration after 2.5 seconds? Something different!) so you cannot treat the entire sprint using the equations governing constant acceleration. You can, however, break the sprint into two parts, each of which can be analyzed with those equations. Parts b and c asked you to consider just the constant acceleration during the first 2.5 seconds and find the velocity and position at the end of that time period. Beyond offering you extra opportunities to show what you’ve learned and possibly hinting at a method of solution, there was no need for me to ask those sub-parts. Indeed, in MasteringPhysics problem 2.21 about the car approaching the stop sign simply asks for the required value of acceleration, leaving it to us to figure out how to break the motion into segments we know how to model.
Please turn in your revised solution, along with any desired corrections, on Wednesday at 9 AM. Feel free to contact me with any questions about this assignment!