You will measure the acceleration of gravity by dropping a picket fence through a photogate. The leading edges of the black stripes are 0.050m apart. As the fence accelerates, the gate will record shorter time periods between stripes. From this information, it will compute displacement, velocity, and acceleration.
Sketch a prediction of a velocity vs. time graph for a freely falling object:
Procedure:
1) Turn on the computer. Connect the USB line from the 750 Interface box to the top port on the back of the computer. Connect the photogate’s plug to channel 1 on the
Interface box. Make sure that the 750 Interface box is on.
Log on.
2) Open Data Studio. Click “Open Activity”. Type “p:\teachers\pasco” and then push the “enter” key, followed by:
Physics Labs
P05 Free Fall
3) Hold the picket fence above the photogate as shown. (Be sure that the picket fence has a soft, foam pad to land on.) Click “start” on the display, then release the picket fence. After the picket fence lands, click “stop”. If picket fence hits the gate, delete the run and start over.
(If you are not sure how to delete the run, ask your teacher.)
4) Open the position and velocity graphs (lower left of screen above the word “histogram”). Click on the displacement graph and click the
“scale to fit” icon at the top left of the display. Click on the velocity graph and then click the “scale to fit” button (above the upper left corner of the graph. Click on the button labeled “Fit” then “linear fit” to get the equation of the best fitting line for the velocity graph only . Record the slope. Print both graphs on the same sheet of paper.
5) Delete your previous run. Repeat steps 3), 4), 5) until each person on the team has had a chance to operate the computer once, and drop the picket fence once. You need not print any more graphs. **When you exit the program, click “ NO ” when asked, “Should Data Studio save this activity?”. That’s “NO.” NO, NO, NO !!

OBJECTIVE: What was the objective of this experiment (sentence, please)?
Acceleration (slope from graph of velocity vs time). Don’t forget the unit!
(show work)
Fi nd the percent error of your average from the accepted value for the acceleration of gravity. (show exp erimental
 accepted calculation). [Percent error = x 100% . Remember this formula!!!!] accepted
Staple print-outs of data and graphs in your lab report.
Questions:
1. Describe two potential sources of the error that you calculated above, not including experimenter (your) errors. (Writing “human error” will cause you to automatically lose one point.)

2. Sketch a graph of position vs time for constant acceleration (down is positive).
3. Sketch a graph of velocity vs. time (down is +) for an object falling from rest, taking into account air resistance .
Bonus: At one of the dots on the position-time graph that you printed, use a straightedge to draw a long tangent to the curve. Find the slope of this tangent line. What does the slope represent? Is your answer verified by your velocity graph? Show calculations and answers below .