OpenStax College Physics for AP® Courses, Chapter 11, Problem 64 (Problems & Exercises)

This is College Physics Answers with Shaun Dychko. We are going to calculate the contact angle between olive oil and glass and we have a glass tube inserted into some olive oil and the capillary action causes the olive oil to raise up a height of 7.07 centimeters which is 7.07 times 10 to the minus 2 meters and we are told the glass tube has a radius of 0.100 millimeters which is 0.100 times 10 to the minus 3 meters. So we start with this formula which says the height raised due to capillary action is 2 times the surface tension of the fluid times cosine of the contact angle between the fluid and the material of the tube— in this case glass— and we divide by the density of the fluid times gravitational field strength times the radius of the tube. So we are gonna rearrange this for cos Θ because we wanna find out what Θ is. So we multiply both sides by ρgr divided by 2 times γ and then switch the sides around as well. So we have cos Θ is ρghr over 2γ and then take the inverse cos of both sides and you end up with Θ is the inverse cos of all this. So we have to look up a lot of information in our data tables. So we have inverse cos of the density of olive oil which is 0.92 times 10 to the 3 kilograms per cubic meter multiplied by g—9.80 newtons per kilogram— times a height of 7.07 times 10 to the minus 2 meters times the radius of the tube divided by 2 times the surface tension of olive oil— and that is... (where's that... right here) 0.032 newtons per meter— and all this works out to 5.1 degrees is the contact angle between olive oil and glass.