# Stoke's Law Problem Set

#### Summary

This is a problem set that involves the calculation of velocities from a Reynolds number, determination of Stoke's Law applicability, and calculation of settling velocities for a variety of grain sizes and materials. This can be used in conjunction with a lab but is itself just a problem set.

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## Context

#### Audience

This problem set is used within a typical, 300-level sed/strat class for geoscience majors. They have previously had at least one introductory geology course, an introductory lab course, and historical geology. There are no math, physics, or chemistry prerequisites, though all students in this particular class tend to have chemistry.

#### Skills and concepts that students must have mastered

Students should be familiar with the equations for Stoke's Law and the Reynolds Number. They should also be familiar with the concept of density and how it varies from material to material.

#### How the activity is situated in the course

We had previously done some small experiments on Stoke's Law and settling velocities. This problem set was originally intended as practice for the test but became expanded beyond that.

## Goals

#### Content/concepts goals for this activity

Stoke's Law and settling velocities. Reynolds number. Non-dimensional. Dimensional analysis.

#### Higher order thinking skills goals for this activity

Relating real properties of materials and fluids to numerical concepts and non-dimensional numbers.

#### Other skills goals for this activity

Students should gaining more familiarity with Excel and with finding material properties online or in reference books. They will get practice with unit conversion, log plots, and data/results presentation. Students should develop better number and scaling senses.

## Description and Teaching Materials

This is a problem set on Stoke's Law. Students should have access to Excel or a similar spread sheet program.
Stoke's Law Practice (Microsoft Word 2007 (.docx) 112kB Jun4 14)

## Teaching Notes and Tips

In class with students with very varied math skills, there were quite a few problems with unit conversions. Students often had trouble determining if there answers actually made sense (i.e., were velocities realistic based on their lab experiments? was anything negative that shouldn't be?).
This activity could be easily modified to work with measurements students take in an accompanying lab or for use with different material properties.

## Assessment

However, the answers were discussed in class along with points of confusion. The answers are easy to generate, so this could certainly be used as a graded assignment.