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This question already has an answer here:

I would test this but I have no tools to test it with.

If I have a beaker of water and weigh it on a measure. Then I stick my fingers in the water (it doesn't over flow) does the weight change or does it pretty much stay the same (excluding fluctuations)

If I were to cut off my fingers then, and let them sink and hit the bottom would the weight change?

If I dropped something in that floated would the weight change?


Lastly, if I were to measure the water in a room filled with air. With a cieling 1 mile tall (atmospheric pressure = 1) and then measure the same water beaker in a room filled with air with a cieling 1 foot tall (atmospheric pressure = 1) would the measured weight change? Not the weight of the water but the weight of anything effecting the scale, including the air in the room, if that pushes down on the scale like I assume it does, I may be wrong

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marked as duplicate by Kyle Oman, ACuriousMind, Danu, Kyle Kanos, Ali Sep 17 '14 at 19:20

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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If you stick your finger in the water, the weight of the finger is still supported by you and so the weight of the beaker does not go up (it goes down a tiny tiny amount because the water rises and the height of the air above it goes down insignificantly.) If you cut off your finger, the weight goes up by one finger because you are no longer supporting it. It does not matter whether it floats or not.

The air is pressing up on the bottom of the scale by about the same as it is pressing down on top of the beaker. That is why you are only weighing the weight of a beaker and not the amount of air above it. The height of the room you are in is not a factor. However, if the beaker is so tall that it is at a different atmospheric pressure at the top then at the bottom then there would be a difference.

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