Science Buddies: "Ask an Expert"

I changed the needle measurement to .045. 1/12= .08333333 (how much drops in one mL)
.08333333 x 7 (drops) = .583333333
.583333333 x 9.81 x 10 to the power of negative 3 = .057225.
Plug into F=2sd.
.057225 = 2s.045
.057225/.09 = .635833333
.635833333 x 1000 = 635.83333 (Converting to dynes/cm)
Why is it off by a hundred?
Also, 4 drops equals to .363333. Why is the change so drastic when the table from the website sticks to around 70?

Hi DiligentWorker,

I think you have an error in your arithmetic where you multiplied the mass of water (0.583 g) by the gravitational constant (9.81 X 10^-3 N/g). The correct result of that multiplication is 0.0057 N, or 1/10 of the value you showed in your post. Using 0.0057 N for the force gives 63.5 dynes/cm (or 0.0635 N/m) for the surface tension.

I hope this helps. Please post again if you have more questions.

A. Norman