- #1
justduy
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Homework Statement
A thin glass plate is pressed at the end of a glass cylinder. The glass cylinder with the glass plate at the bottom is dipped in water so that the plate is 25 cm under the water surface (The glass cylinder i open, meaning only the bottom part is closed, due to the glass plate). They we proceed with filling this cylinder with Ethanol, and the question is: how much Ethanol must we fill until the plate loosens. It asks for the height of Ethanol, meaning how high must we fill it.
(I realize that this is not the easiest way to describe the problem, but being that my English is not that good, this is the best I can do. Sorry in advance)
Density of Ethanol: 0.79 * 10^3 kg/m^3
of Water: 1.00 * 10^3 kg/m^3
The Attempt at a Solution
I don't really know, I looked at the proposed solution, but I understand nothing. The book never said anything else about this. The proposed solution said that the plates loosens when the pressure of water = pressure of ethanol, basically: D(water) * g * h (25 cm) = D(ethanol) * g * h (this is what we are supposed to find).
I don't understand why...