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Re: [Phys-l] buoyancy on a submerged pole



At 6:59 AM -0700 11/5/10, John Mallinckrodt wrote:
Chuck Britton wrote:

My hypothesis (which I am QUITE ready to have disproved -
experimentally) is that SuperGlue or threads will exert the SAME
upward force on the bottom sheet of glass.

It seems to me that you are hypothesizing a situation where the BOX is subject to only the following three forces

1. A gravitational force (DOWNWARD)

2. A net force due to the fluid that presses on the sides and the top of the box (DOWNWARD)

3. A force due to the glue that attaches the box to the aquarium bottom and excludes water from underneath the box (DOWNWARD)

yet somehow manages NOT to accelerate downward.

Have I misunderstood the hypothesis? Are you imagining some other force that is acting on the box? If so, what is it?



I THINK that my hypothesis can be restated as saying that an object submerged in a fluid will experience an UPWARD force that is equal to the weight of the fluid displaced.