Objects that float at the interface between a liquid and a gas interact because of interfacial deformation and the effect of gravity. We highlight the crucial role of buoyancy in this interaction, which, for small particles, prevails over the capillary suction that often is assumed to be the dominant effect. We emphasize this point using a simple classroom demonstration, and then derive the physical conditions leading to mutual attraction or repulsion. We also quantify the force of interaction in particular instances and present a simple dynamical model of this interaction. The results obtained from this model are validated by comparison to experimental results for the mutual attraction of two identical spherical particles. We consider some of the applications of the effect that can be found in nature and the laboratory.
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September 2005
PAPERS|
September 01 2005
The “Cheerios effect”
Dominic Vella;
Dominic Vella
Division of Engineering and Applied Sciences, Harvard University, Pierce Hall, 29 Oxford Street, Cambridge, Massachusetts 02138
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L. Mahadevan
L. Mahadevan
Division of Engineering and Applied Sciences, Harvard University, Pierce Hall, 29 Oxford Street, Cambridge, Massachusetts 02138
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Am. J. Phys. 73, 817–825 (2005)
Article history
Received:
November 22 2004
Accepted:
February 25 2005
Citation
Dominic Vella, L. Mahadevan; The “Cheerios effect”. Am. J. Phys. 1 September 2005; 73 (9): 817–825. https://doi.org/10.1119/1.1898523
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