Experiment 1: Fluid Statics

Objective:

The objective of this experiment is to find out the buoyant force using 3 different ways. Students will compare the three results and determine the most accurate method. Underwater weighing method, displaced Fluid Method, and volume of Object Method will be used.

A.      Underwater weighing method

W_air= 1.13N±0.005N

W_water=0.67N±0.005N

B=Fw-Ft

B=1.13-0.67=0.46N±0.005N

B.      Displaced Fluid Method

Beaker m: 0.15086kg±0.000005kg

Beaker+water m:0.19177kg±0.000005kg

Water m:0.04091g±0.000005kg

The uncertainty of Buoyant force=⊿m*g=0.000005*9.81=0.00005kg

Wf=B:0.4009N±0.00005kg

C.      Volume of Object Method

V=r²hπ

h=0.076m±0.0005m

D:0.02m±0.0005m

V=3.73*10^-5m³

W_f=pgv

p=density of water=1*10³kg/m³

The uncertainty of Buoyant force=((p*g*π*2*h*r*⊿r)^2+ (p*g*π*r²*⊿h)^2)^0.5

=((1*10³*9.81*π*2*0.076*0.01*0.0005)^2+(1*10³*9.81*π*0.01²*.0005)^2)^0.5=0.0234N

W_f=B=0.366N±0.0234N

Summary

1.      uncertainty of A:0.005

Uncertainty of B: 0.00005

uncertainty of C:0.0234

Percentage uncertainty of A:0.005/0.46=1.09%

Percentage uncertainty of B:0.00005/0.4009=0.0147%

Percentage uncertainty of C:0.0234/0.366=6.4%

From the result, B is the most accurate since the percentage uncertainty is the smallest.

2.      I think the underwater weighing method is the most accurate method because there is less variables. In the displaced Fluid method, since mass of water dripped from the overflow spout has to be used to determine the buoyant force, there is inaccuracy. No advanced equipment is used. Human error may appear. For the volume of object method, since the height and diameter of the cylinder were measured by ruler instead of advanced equipment, inaccuracy appeared.

3.      If the cylinder is touching the bottom of water container in underwater weight method, the value for the buoyant force would be smaller. When the bottom is touched, an upward normal force is applied. B=W-T-N. The buoyant force would be smaller.