Falling Bodies and Terminal Velocity

• Pre-Lab Checklist
• Experiment Notes: Things to keep in mind while performingthe experiment.
• Analysis Notes: Questions to answer in your analysis of theexperment.
• Grading Breakdown
• Return to Physics Lab home page.

Pre-Lab Checklist

1. In your own words, describe the situation to be studied.

2. List and define each of the parameters to be measured directly.

3. List the quantities which will be calculated.

4. List any graphs you will need to create in your analysis of theexperiments.

Experiment Notes

PART A.

1. You are using the Pasco Interface instead of the BIB interface. Thereforeyou will need to change procedures 1 to the following:
   • Click and drag the stereo-plug icon to Digital Channel #1. A dialog box will pop up asking you to choose a digital sensor. Choose the motion detector.
   • Choose the trigger rate = 50Hz.
   • Click and drag the graph icon to Channel #1 also. Choose position so that the graph will show position versus time.
   • Click on the vertical axis to choose the range: Max=0.0m and Min=0.0m.
   • You are now ready to take data. Click on the REC button to record a data set. Click on the STOP button to stop taking data. The MON button lets you monitor the data without saving any data.
2. It takes a bit of practice to get the ball to bounce beneath the motiondetector in such a way as to show several complete bounces. If you continue tohave problems taking the data, talk to your TA. A clean set of data shouldshow a horizontal line when you are holding the ball at rest before release, ahalf-parabola for the original fall to the floor, and then a series of eversmaller parabola's as the ball bounces in place before coming to rest.
3. When saving your file, name the files in the following manner: a:/bounce1.sws The a:/ will send the file to your disk in the a: drive.
4. Procedure #4 as written in the lab manual applies to the BIB interfacerather than the Pasco interface. Use the following procedures to obtain aparabolic fit of your data.
   • In the lower left-hand corner of the graph window is a set of buttons that can be used in the analysis of the data. In order to make a mathematical fit of your data, click on the Sigma button. This will open up a statistics sub window to the right of the graphed data.
     
   • To make a parabolic fit of the data, use the pull-down menu in the statistics sub window, first choosing CURVE FIT and then POLYNOMIAL FIT. The statistics will be shown in the stats sub window below the button for the pull-down menu. A plot of the best fit curve will also appear in the graph with your data.
     
   • To find the acceleration for the ball during a single bounce, click and drag the cursor to enclose the data from one bounce only.
     
   • Remember that the kinematic equations describe the position versus time relationship for motion at a constant acceleration as: x_f=x_o+v_ot+0.5at² Compare this to the parabolic fit of one bounce on the x vs. t plot of your data to calculate the acceleration of the ball during that bounce.
5. Procedure #5 as written in the lab manual applies to the BIB interfacerather than the Pasco interface. Use the following procedures to obtain alinear fit of the velocity versus time data.
   • To create a velocity versus time graph for your data, click and drag the graph icon to Channel 1, just as you did before. This time, however, choose velocity to obtain a velocity versus time plot. You should see a sawtooth shaped graph.
     
   • Highlight the data from one of the upward sloping sections of the data to see the acceleration during a particular bounce. Try to look at the data on this graph which coresponds to the bounce you used in Procedure 4.
     
   • Use the statistics pull-down menu, choosing CURVE FIT and then LINEAR FIT to obtain the best fit straight line through the highlighted section of the data.
     
   • Remember that the kinematic equations describe the velocity versus time relationship for motion at a constant acceleration as: v_f=v_o+at Compare this to the line fit of one bounce on the v vs. t plot of your data to calculate the acceleration of the ball during that bounce.
     
6. Due to time considerations, omit Procedure #6 and use the following datatable rather than the one given in the lab manual.

   .

   Table 1. Falling Bodies

   Ball #	Graph	Fit Equation	Acceleration (m/s2)
   1	x vs. t
   1	v vs. t
   2	x vs. t
   2	v vs. t

.

PART B.

1. Be very careful in the release of the coffee filters. If you pull yourhands away too quickly, they will generate enough of a breeze that the filterswill develop a significant wobble as they fall. The more cleanly you canrelease the filters, the better the data set will be.
   
2. Don't release the filters until after you hear the ranger begin to clickand you see a horizontal line appear on the screen. This horizontal section ofthe data will mark the position of the filters before their release.
   
3. When making your parabolic fit of the data, highlight the data from a fewsecond before release to the point on the data where you see it become linear.Try this a couple of times until the plot of the fit best matches the graph ofyour data.
   
4. When making the line fit of the data to find the terminal velocity,highlight only that data at the of the end of the run where the filters are falling at a constant speed. Again, try this a couple of times until the plotof the fit best matches your data
   

Analysis Notes

1. Your results section should include the average acceleration for each ofthe two balls and the terminal velocities for each of the four sets of coffeefilters.

2. Describe the graphs that you obtain for the falling balls and the fallingfilters. How are they similar? How are they different?

3. Compare the accelerations of the two balls. Does the diameter of the ballaffect the measured acceleration of the motion? Explain why you think this isso.

4. Explain how you determined the location at which the filters reachedterminal velocity. Did the number of filters affect how far the filters fell before reaching terminal velocity? Explain why you think this is so.

5. Explain how you determined the terminal velocity reached by each set offilters. Does the number of filters affect the terminal velocity reached? Explain why you think this is so.

Grading Breakdown