Here are our results for several different materials. Do not worry if your angles are not quite the same. There is likely to be a certain amount of variation in granular materials in different areas of the world.
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Angle of Repose (degrees)
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| Material |
First Pour |
Second Pour |
Third Pour |
Average |
Brown sand
|
33
|
33
|
32
|
32.7
|
White sand
|
34
|
32
|
33
|
33
|
Salt
|
35
|
35
|
35
|
35
|
Sugar
|
37
|
35
|
36
|
35
|
White rice
|
40
|
39
|
39
|
39.7
|
Brown rice
|
40
|
43
|
41
|
41.3
|
Lentils
|
39
|
34
|
39
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37.1
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We noticed that larger granules seemed to produce a steeper angle of repose than smaller granules. We also noticed that the readings for the smaller granules were more consistent than the readings for the larger granules.
What do you think would happen if you poured a mixture of two granular materials with different angles of repose into your Hele-Shaw cell? For example, what would you expect to see if you poured a mixture of white rice (angle of repose of about 40 degrees) and salt (angle of repose of about 35 degrees)?
Make your prediction and try it yourself. The results might surprise you. Click here to see a photograph of our results.
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Virtual Experiment
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The shapes and sizes of the two kinds of grains make a difference in the results. How quickly you pour the mixture into the cell may also affect the results. Try different granular mixtures and see what happens. Take pictures and send us your results.
Test out a virtual Hele-Shaw cell. Use your protractor to measure the angle of repose of the different materials. What can you infer from your measurements?
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