Buoyant Force and Density: The Physics of FloatationLuke ReaginsAward: Top 100
School: mamaroneck high school The concept of buoyancy is unique in its ability to explain why an object floats or sinks. In this experiment I placed a peeled orange and an unpeeled orange in identical glasses of water to demonstrate how changes in density affect buoyancy. In general, if the density of an object is greater than the density of water, an object will sink. If the relationship is opposite, and the density of an object is less than that of water, it will float. The unpeeled orange floats because the water exerts an upward buoyant force on it which is equal to the force of gravity. When the orange is peeled, the density changes. The peel of the orange contains air pockets, which makes the unpeeled fruit less dense than water. This helps it to float. When peeled, the orange loses its skin, leaving behind the flesh of the orange which has a density more similar to the density of the water in comparison to the unpeeled orange. With less air and a higher density, the peeled orange displaces less water and may sink lower into the water. This experiment demonstrates how small changes in an object's density--like removing the peel--can significantly affect whether it will float or sink. 
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