Archimedes’s Principle of Force of Buoyancy Lab

Qiliang Huang

Per. 4

Physic

Purpose:

l Verify Archimedes’s principle

l Calculate ρ of unknown fluid

Theory:

l According to Archimedes’s principle when object suspended by fluid, the fluid apply force to the object that’s equal to the fluid displace, call buoyant force.

l When object sinks, their velocity is impeded by the fluid, is the acceleration of this resistance related to the buoyant force.

Equipment:

Small graduated cylinder

Large graduated cylinder

Balance

Beaker

Greased pencil

Micrometer

Marbles

Dense object (fisher weight)

Flowing object (paraffin)

Meter stick/ruler

String/thread

Stop watch

Fluid

Procedures:

1. measure the height of small and large graduated cylinders

2. calculate the time the marbles should take to fall from the top of each cylinder to its bottom

3. take the small cylinder, measure its empty mass then partially fills it with water; measure the change in mass and get the volume of the water

4. fill the large cylinder with water

5. measure the mass and radius of several marbles

6. measure the time it takes the marble to fall through the water in the large cylinder, repeat this step for 3 trials

7. take a small cylinder and measure the time for a marble, that you have measured its mass and radius, to fall through an unknown fluid

8. measure the mass of the fisher weight and its volume via the small cylinder

9. fill the beaker with water, and hang the fisher weight into the water then measure the wet mass

10. measure the mass of the paraffin

11. measure the combined mass of fisher weight and paraffin and its volume in a beaker

12. measure the wet combined mass of fisher weight and paraffin

Diagram:

Data:

Recorded Data

Height

Time of falling marble

Mass

Mass w/39.2 mL of unknown fluid

Small graduated cylinder

18.3 cm

0.19 s

88.5g (no water)

134.13g (46.4 mL of water)

127.9g

Large graduated cylinder

42.5 cm

0.29 s

	Radius	Time to fall through water(L/cylinder)	Mass	Time to fall through unknown fluid
Marble 1	7.605mm	0.60s	5.200g	179.44s
Marble 2	7.575mm	0.56s	4.917g
Marble 3	7.500mm	0.47s	4.891g
Average	7.560mm	0.54s	5.003g

	Empty mass	With soap mass	Volume of soap	Falling time of marble 1
Small cylinder	88.2g	127.9g	39.2 mL	2.59.44

	Volume	Mass(dry)	Mass(wet)
Fisher weight	0.0000018 m³	22.92g	20.885g
Paraffin	0.0000132 m³	12g	0g
Combined	0.000015 m³	34.92g	19.640g

Calculated Data

	Density
Water	983.00 kg/m³
Unknown fluid	1005.00 kg/m³

	F_B via ρgV	F_B via F_T	% variance	% error	ρ of object
Fisher Weight	0.01740 N	0.01995 N	13.88%	1.29%	12733.34 kg/m³
Paraffin					909.10 kg/m³
Combined	0.14470 N	0.14970 N	3.39%	1.61%

	Volume	F_B via ρgV	F_B via ma
Marble _avg	1.8100 • 10^-6m³	0.01750 N	0.03450 N

Analysis and Calculation:

_________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Conclusion:

A. Source of error:

equipment error

calculation error

timing error

fiction of fluid

impureness of water

air bubbles take up volume in the unknown fluid

B. New principles learned:

C. What section of the data does not seem to make sense. Describe clearly and solve the discrepancy: