Discussion: A body immersed in a fluid is buoyed up by a force equal to the weight of the fluid the object displaces
Purpose: Use of the CBL to discover the principles of buoyancy and to reinforce the idea of density, displacement and weight
Materials: CBL, TI-82,Dual Range force probe, string, graduated cylinder, known objects, clay, picture setup
Preliminary questions
1. When you place an object into the fluid? What do expect to happen to the fluid?
2. What do expect to happen to the mass, weight, WHY
3. Will there be a greater overflow due to a larger object? A heavier object?An Object of differing shapes?
Procedure: PART ONE
1. Set up the equipment as shown
2. Fill the graduated cylinder to approximately half full
3. Connect force probe to channel one on CBL
4. Connect TI-82 to CBL using link cable, and turn on
Press program, press #1 Physics-enter
Main menu press #1(set up probes)
Press #1 number of probes, press #2 for force probe, #3 for 10N probe
Enter channel #1, calibration press#1(perform new)
Enter 0, place 500 g(4.9N)on probe and enter 4.9 on TI-82
Main menu- #2 collect data
5. Place mass on string, hang on force probe above half filled graduate cylinder
Press #3 (Trigger/prompt)
6. Press trigger, follow directions
7. Lower cylinder into water 1/4 way,trigger,1/2, 3/4, and then completely submerged
press #3 graph data
8. Repeat 3 more times
DATA: Temperature of water__________ Density___________
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Trial |
volume of displaced water |
Force Before |
Force after |
difference |
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1 |
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2 |
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3 |
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4 |
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average |
Calculate the weight of the displaced water using: ml of water X density X =_________
PART TWO
Repeat Part One using a different object and placing the data in table #2
|
Trial |
volume of displaced water |
Force Before |
Force after |
difference |
|
1 |
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|
2 |
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|
3 |
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|
4 |
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average |
PART Three
8. Using a piece of clay make the clay into a ball
9. Using the procedure from part one determine its weight(force) before and after submersion . Before____________ After_____________
10. Mold the clay into different shapes and determine the force when placed into the water . Examples: triangle, flat, open rectangle, open square, etc.
SHAPE FORCE
__________ _________
__________ _________
__________ _________
Conclusion:
Questions
1.How does the buoyant force on a submerged object compare to the weight of the fluid displaced?
2. How does the volume of water displaced by the floating clay compare to the water displaced when it sank? WHY?
3.Suppose you are in a hot tub floating on an air mattress. If you fall off, will the water level in the tub rise or fall? Explain your answer.
4. Devise an experiment to test your prediction in the laboratory.
Extensions
1. Use the method described to determine the density of a liquid
2. Determine the density of an object that floats
