Buoyant force
The fluid pushes on all sides of a submerged object. However, because pressure increases with depth, the upward push on the bottom surface (F2) is greater than the downward push on the top surface (F1). Therefore, the net buoyant force is always upwards.
Source
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"OpenStax College, College Physics. November 3, 2012."
http://cnx.org/content/m42196/latest/?collection=col11406/latest
OpenStax CNX
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