INTRODUCTION: The object of this lab is to compare the terminal velocities of an object falling through various mediums.
EQUIPMENT:
1-2 meter plastic tube
fishing weight and fishing line or string
smart pulley, ULI box
various liquids(motor oil, vegetable oil, water, soap, etc.)
paper towels or wet wipes
SET-UP: These pictures shows the set-up of the equipment.
 |
 |
|
|
This is the basic setup for my lab..... |
...here is a close-up of the weight pulling the string over the Smart Pulley. |
PROCEDURE:
1. Use a tube that is at least one meter in length and is sealed tightly at one end. The tube shown here is 1.5 inch PVC pipe and is 1.75 meters in length.
2. Arrange the smart pulley over the top of the tube and plug into the ULI box .
3. Cut a piece of string that is about 30 cm longer than your tube and tie on the fishing weight.
4. Set up your computer using Logger Pro to display the graphs of s vs. t, v vs. t, and a vs. t.
5. Place the fishing weight and string over the pulley and let the weight hang just above the top of the fluid and have one partner hold it in place.
6. While one partner clicks the collect button, the other partner should let go and allow the weight to fall through the tube filled with some liquid. The fishing line needs to stay on the pulley so you may have to redo the trial if the string comes off the pulley. Use the paper towels or wet-wipes to clean the fishing line or string before placing it back on the pulley! The wet wipes work best for the oily liquids. When using fishing line you will want to stretch out the line overnight to eliminate any kinks in the line and allow it to travel smoothly over the pulley.
7. Print a copy of the graphs and repeat these steps for various liquids.
QUESTIONS:
Look at one set of your graphs and answer the following:
1. How does the s vs. t graph indicate constant acceleration? Constant velocity?
2. How does the v vs. t graph indicate constant acceleration? Constant velocity?
3. How does the a vs. t graph indicate constant acceleration? Constant velocity?
4. How long does it take for the object to reach a constant velocity?
5. What does the slope of the v vs. t graph tell you?
6. What do you call the constant velocity that is reached?
7. Using a force diagram, explain why the object would stop accelerating?
8. Would the graphs of a skydiver's motion look similar or different? Explain.
9. How would the graphs for a small skydiver and a large skydiver differ?
10. Why don't raindrops kill you after falling for such long distances? Would you want to be in a rainstorm on the moon? Why?
Look at all of your graphs and answer the following:
1. How do the graphs compare for the differing liquids?
2. What do the graphs tell you about viscosity?
3. How does viscosity affect terminal velocity?
Go to teacher supplement
lab written by Angela Glidewell@The Woodlands H.S.