Experiment 05
FREE FALL
PROCEDURE
1.    Open up the Freefall Workbook and fill in the header information.

2.    The photogate should be already connected to the interface box, which is in turn connected to the computer. Open the Picket -Fence application.

Note that all measurements will be made in SI units (m, s, kg). Move to the Distance vs. Time Graph Window.

3.    TEST RUN: Use the mouse to hit the Collect button. The timer will not begin until the photogate beam is interrupted. As a test run, drop the picket fence lengthwise through the jaws of the photogate so that the ruler is as vertical as you can get it. Also practice making a "clean" release; that is, gently hold the tip of the ruler between thumb and forefinger and let it suspend itself along the vertical, then smoothly release it so that it falls without wobbling. Please make sure that it lands on the foam cushion to avoid damaging it. Hit the Stop button after the ruler has landed.

4.    The data will be taken automatically, and plots of Distance vs. Time and Velocity vs. Time (magnitude) will be displayed. A TableWindow, with the data tabulated will also be displayed. If either of these windows are missing, select the appropriate one under the WINDOW menu.

5.    Select the Velocity vs. Time window, and under the ANALYZE menu, confirm that the following items are checked: Linear Fit and Statistics. These selections will tell the computer to draw a straight line that best fits the data through a technique called least squares fitting (linear regression), and to evaluate the slope and y-intercept of this line.

6.    MEASUREMENT RUNS: Make 10 drops of the picket fence through the photogate. For each run, perform the following steps before going on to the next one:
 

On the Table Window, select the Acceleration column, and use EDIT...COPY to place it on the Clipboard.

Move to the Worksheet window and EDIT...PASTE the Acceleration data at the first cell indicated for each run.

Record the Slope and the Y-Intercept (as displayed in the floating information box) on the Worksheet in the indicated cells.
 
 

7.    After the 10th run is completed, hit the expand button on the Distance vs. Time window so that it fills the entire screen, as illustrated below:

Select ANALYZE...Examine and ANALYZE...Tangent, and place the cursor at a point near t = 0. Record the time value, the distance value, and the value of the tangent line slope from the display box on the Worksheet in the cells indicated. Repeat for a point near the right end of the plot.

8.    Obtain a print-out of the Worksheet by selecting the Excel window and choosing FILE...PRINT.