Answer Happy

Procedure For this experiment, you will need a hard yet smooth surface about the size of your text- book (e.g., clipboard, kitchen cutting board, whiteboard), two hard objects about the size of a large marble (e.g., rocks, compacted soil, metal washers/hex nuts), a small amount of water and a cup, and a protractor to meas- ure angles. If you don't have the protractor, trace the one provided below (Fig. GL9.1). Use these materials to perform the following experiment and answer the questions. 1. With your materials replicating a rock or soil clump positioned on a slope, use the protractor to calculate the slope angle indicated by angle a. 2. With your "slope" lying flat on a table and your "rock" positioned near the top, slowly and gently tilt the slope upward until rock exceeds its angle of repose and begins to move downward (Fig. GL9.2). Record that angle when the object first moves. Repeat this 10 times to simulate the variable condi- tions in the real world. Object A 1 2 3 4 5 6 7 8 9 10 Trial Angle
3. Calculate the average for the 10 trials. Average angle of repose for Object A 4. Repeat the steps for Object B. Object B 1 2 2 3 3 4 5 6 7 8 9 10 Trial Angle Average angle of repose for Object B =
5. Was there any difference in the angle of repose for your two objects? 6. Explain any similarity or difference. Place object A near its average angle of repose (but not allowing it to slip). With your fingers or a hard object (e.g., tool, rock, wooden stick), rap the middle of the board a few times. 7. What happens to the angle of repose? 8. What natural phenomena did your rapping simulate? Moisten your "slope" and repeat the tilting procedure again with both objects. Then repeat this process after moistening both the slope and your object.
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AGL9.2 Slope angle Slope Object on slope Protractor