Experiment	1	2	3	4
Angle of repose of rice	38°	41°	38°	40°
Angle of repose of mung beans	29°	36°	31°	31°

The results of the four experiments are different, with Experiment 2 yielding the highest angle of repose for both rice and mung beans. Since the angle of repose is the maximum angle at which a pile of unconsolidated material can remain stable, therefore the method producing the greatest angle should qualify to be the most recommended one. From the results above, we can see that the method in Experiment 2 is the best out of the three.

In Experiment 2, highest angle is recorded before downward movement of particles occurs

Explanation:

Experiments 1 & 3 involved the downward movement of particles before the angle of repose was established. In Experiment 1, the particles rushed down from the funnel and would continue its movement by their momentum. In Experiment 3, the flow out of the jar would drag other particles with its force. In Experiment 4, there was also movement of particles but more under control. However, the final lifting of the can would leave a flat top on the pile and a convex slope. But in Experiment 2, there was no flow of particles in the cylinder because the rolling of the cylinder was stopped as soon as the particles began to show the tendency of falling.

These experiments involve the downward movement of particles before angle of repose is established

Other Comparisons

The highest possible value in the results is an important criterion for evaluation, but the four methods could also be compared in terms of their cleanliness and ease to use. The second experiment has everything inside the container and so it would not cause a mess. It is also easy to use because the container is all you need. On the other hand, Experiment 1 needs more efforts to clean up, and Experiment 3 requires more equipment to complete. Both of them are not as desirable as Experiment 2.


Ratings on the Experiments

I wanted to see how the four experiments compared with one another. The following table shows the ratings I gave to the different methods.

Experiment	1	2	3	4
Greatest angle	1	4	2	3
Cleanliness	1	4	3	2
Easy to do	3	4	1	2

The Final Verdict

Amongst the total ratings from the table for the experiments, the method in Experiment 2 has the highest score, with the highest rating for all three criteria. Therefore that method is highly recommended to be used to measure the angle of repose of different particles, especially in the classroom or at home.

However, it should be noted that the results produced in Experiment 2 could only be achieved in a controlled environment with no down-slope movement of particles. In reality, angle of repose is usually formed by particles falling from above (e.g. a talus slope under a cliff formed from rockfalls). Therefore the methods of Experiments 1 & 3 resemble more what actually would happen in the real environment although they do not achieve the greatest angles in their results.