|MadSci Network: Physics|
When any object is placed in water there is an upward force referred to as a force of bouyancy. If the mass of water displaced by an object is equal to the mass of the object doing the displacing, then the object floats or the weight of the object is equal to the force of bouyancy. Another way to think of it is if the density of the object, its mass divided by its volume, is less than the density of water, then the object will float. For reference, any physics text and most science texts will include a discussion of bouyancy. So, if a steel can is empty or contains something lighter than water the can floats. Thanks for the question.
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