Question

A layer of oil 1.50 mm thick is placed between two microscope slides. Researchers find that a force of $5.50 \times 10^{-4} \textrm{ N}$ is required to glide one over the other at a speed of 1.00 cm/s when their contact area is $6.00 \textrm{ cm}^2$. What is the oil's viscosity? What type of oil might it be?

Final Answer

$0.138 \textrm{ Pa}\cdot\textrm{s}$

This is olive oil.

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Video Transcript

This is College Physics Answer with Shaun Dychko.
Fluid viscosity is measured by moving some flat plate of some area over a layer of fluid with some thickness l, at a certain speed. You have to measure what force it would take to do that and then combine those numbers according to this formula and you end up with the viscosity. So we multiply the force by the thickness of the fluid layer that was 1.5 millimeters, which we convert into meters by multiplying by ten to the minus three. We have 5.5 times ten to the minus four Newtons, multiply those two and then divide by one centimeter per second converted into meters per second, then multiply by six square centimeters converted into square meters by multiplying by one meter per 100 centimeters twice, then we get 0.138 pascal seconds. According to table 12.1, this must be olive oil.