# Homework Help: Surface tension and the volume of drops

1. Aug 14, 2010

1. The problem statement, all variables and given/known data
For a capillary, or a thin glass rod, the surface tension of a drop on it's end is given by T=kmg , where k is some constant which depends on the radius of the capillary or rod, and mg is the weight of the drop.
After experimentally finding values for the volume of the drops formed at the end of some rods, plot the volume of the drops against the radius of the rods used.
If there is a linear portion in the graph, find the value of k from it.

2. Relevant equations
T=kmg

3. The attempt at a solution
I got a graph that is linear, passing (approximately) through the origin. Now, I know that mass=volume*density, therefore volume is proportional to the weight of the drop, and hence proportional to the surface tension (from T=kmg). But I cannot understand how to get the value of k from the graph. All I understand about the graph is that it should pass through the origin (because when the radius of the rod =0, the volume of the drop is obviously 0).