Chapter 11, Problem 60PE

What fluid is in the device shown in Figure 11.29 if the force is $3.16\times {10}^{-3}$ N and the length of the wire is 2.50 cm? Calculate the surface tension $\gamma$ and find a likely match from Table 11.3.

Figure 11.29 Sliding wire device used for measuring surface tension; the device exerts a force to reduce the film's surface area. The force needed to hold the wire in place is $F=\gamma L=\gamma \left(2l\right)$ , since there are two liquid surfaces attached to the wire. This force remains nearly constant as the film is stretched, until the film approaches its breaking point.