Understanding Graphs of Motion
 
Part III, Testing your Understanding of x, vx, and ax

•    Open the Logger Pro file for Part III, and then try to move the cart in such a manner as to match one of the following four prescriptions for at least a two-second time duration, repeating as necessary in order to accomplish the prescription.  You can Autoscale them with the “A” button in the top ribbon of the Logger Pro window.  If you have time, each student partner should do all four of the following prescriptions.  If you have fewer than fifteen minutes left, you should each take a pair of prescriptions.

1.    x increasing, vx reasonably constant
2.    x decreasing, ax positive
3.    vx positive, ax positive
4.    vx negative, ax negative

•    When you have good data for each of the four prescriptions, copy and paste an example into the box below Question 2 of your worksheet, following the instructions for Question 2.

•    In this part, only x(t) and vx(t) are plotted (ax(t) is not).  The reason for this is that vx(t) and ax(t) values are GENERATED from the x(t) data (which are actually MEASURED – by the motion detector), vx(t) through one process called numerical differentiation, and ax(t) through two such processes, with the result that a lot of noise shows up in the ax(t) data.  In subsequent experiments you will be shown a sophisticated, computer-appropriate way to extract excellent average acceleration values from the Logger Pro data at hand.

•    Yet you only need the x(t) and vx(t) graphs in order to figure out how to match these various prescriptions, even if acceleration is prescribed!  How indeed?  In fact, all you really need is the x(t) graph OR the vx(t) graph!  If you don’t understand this point, be sure to ask your lab instructor about it if you and your partner cannot figure out the answer by yourselves.

Congratulations! You have almost finished your first introductory physics experiment with equipment.  Each partner now only needs to respond individually to Questions 3 and 4 of the worksheet and submit it through myWPI.  Make sure to change the order of your name and your partner's name at the top of the worksheet for your respective copies.  Email them to yourselves such that you have a record of your work in case of any problems with submission for grading.  To submit them, each student must log on to the section's myWPI site, select Lab Submissions in the left-hand menu, click on the appropriate link, and attach the local file (your worksheet).  Internet Explorer is the most reliable means of submission.

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