Valori sperimentali raccolti

Materiale utilizzato

• a water basin
• lycopodium powder
• oleic acid (ρ_{oleic acid} = (8,73 ± 0,01) · 10^-1 g/cm ³ = (8,73 ± 0,01) · 10² kg/m ³) in solution 1/10000 with hexane
• a calibrated pipette (sensibility 0,01 ml = 0,01 cm³) to drop the solution of oleic acid and hexane

Taking data

We prepared the basin spreading the lycopodium powder on water, then we dropped some oleic acid on it, we waited some seconds to make the spot stabilize, then we measured its area with various methods.

The entire experiment has been repeated two times.

During first experiment we obtained a spot with a strange shape, like this:

We measured the area of the two "branches" ("braccio" in the picture) with millimeter paper, and the area of the circle ("cerchio" in the picture) was measured by measuring its diameter with a meter (sensibility 0,1 cm); however, we had to this measuration from a big distance, so we used the maximum and minimum valor to calculate error.

Second misuration was taken reporting its shape on a lucid sheet and then on a millimeter paper. Then, we measured its area by counting the squares correspounding to 1/4 of a square centimeter. This is the shape of the spot:

Obtained data is indicated here (S is the area of the spot, d is the diameter of the circle and V is the volume of the spot):

The mean valor between an interval of areas [val min ; val max] is taken as the most likely; its error is half the interval:

The operation for the diameter is the same.

For the first spot, the area of the circle is calculated, then it is calculated the error:

The total area is the area of the branches plus the area of the circle.

Remembering that we used a 1/10000 solution, the volume obtained is divided by 10000, and so is its error.

This is the data table: