Effect of Colloidal Particles on a Drop

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According to the principle of free fall, only gravity acts upon an object in midair. However, as with all scientific principles, free fall plays out differently in practice. In my experiment, I first tested to see the effect of changing the glycerol weight-percentage of a drop of glycerol-water on its maximum spread when dropped onto smooth glass at each given height, greater spread indicating greater kinetic energy present within the drop. Turns out, glycerol weight-percentage is inversely related to maximum spread. Moreover, the greater the glycerol weight-percentage, the higher the viscosity of the drop due to higher friction between drop particles, and the smaller the potential spread of the drop. Next, I performed a similar experiment on colloidal suspensions. Colloid weight-percentage is also inversely related to maximum spread of the drop at each height dropped. However, as colloidal suspensions are non-Newtonian fluids, they lack a linear relationship between viscosity and shear stress, which results in equal spread for a dilute colloidal suspension and water, disrupting the trend of greater spread for lower colloid weight-percentage. Also, due to the fact that colloidal suspensions are composed mainly of water with particles suspended and that water has low viscosity relative to glycerol-water, colloidal suspensions show greater maximum spread than does glycerol-water at each height dropped. As a result of completing this project, I primarily gained a first-hand understanding of how the principle of free fall plays out in real life using different concentrations of glycerol and colloids in water.

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  • 06/03/2019
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