Say for example, you've got an aquarium that weighs 100 pounds when full of water. If you were to float a 10 pound object inside of that aquarium, does the whole system now weigh 110???
Do Floating Objects Have 'Weight'?
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To an external observer, yes. The mass is cumulative.
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If you put a ten lb rock in and no water is displaced out, then the systems weighs in 110 lbs. If the tank were full to the brim and some water ran out when the rock was placed in then then it would weigh a 110 lbs less the weight of the water that overflowed.Say for example, you've got an aquarium that weighs 100 pounds when full of water. If you were to float a 10 pound object inside of that aquarium, does the whole system now weigh 110???
Similarly, if you float a ten lbs block of wood in, the system would weigh 110 lbs., but if the tank were full to the brim and some water ran out when the wood was placed in then then it would weigh 100 lbs, since 10 lbs of water would have overflowed the tank.
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DevonDiver
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sam1
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This question reminds me (if I remember correctly) of the question Charles Lindbergh asked himself while flying the Atlantic: does a (house)fly flying (as opposed to sitting) in the cockpit add weight to the aircraft? (Answer: yes.)
As long as the aquarium is in air, the cumulative wt would be 110#.
If you were to weigh the object in the tank of water however it would weigh less than it would in air (depends on the density of the object). Objects are either positive or negative boyant.
If you were to weigh the object in the tank of water however it would weigh less than it would in air (depends on the density of the object). Objects are either positive or negative boyant.
Assuming you have a scale under the tank then yes.
If say you have it half full and add a 10lb piece of wood and no water over flowed then yes it would be 110#. Even thou the water is pushing up on the wood it is still pushing down its self.
Test it out man.
If say you have it half full and add a 10lb piece of wood and no water over flowed then yes it would be 110#. Even thou the water is pushing up on the wood it is still pushing down its self.
Test it out man.
2 Big 2 Fail
Contributor
Of course, if you want to get picky (and you know how we love to get picky), if depends. The weight of any part of the aquarium/water/log system is a function of mass and gravity. The gravity part changes with distance from the Earth's center. That distance from center varies with location because of the equatorial bulge. Plus, on the equator, the speed of a point on the surface is faster than toward the poles, so centrifugal force counter acts gravity to a greater degree and further lessens apparent weight. And that's ignoring the effects of the moon whose own gravity effects objects on Earth.
So, when you place the log into the aquarium, some of the water is displaced upward, becoming ever so slightly less weighty. And unless you've figured the weight of the log to be ten pounds at precisely the altitude it will assume in the aquarium, it will be very slightly more or less than ten pounds where it ends up.
Of course, using pound to express weight can be misleading. Pound can be a measure of mass or a measure of force. When you use a scale, you are measuring mass, and it is meaningful only if you calibrate the scale locally.
So, when you place the log into the aquarium, some of the water is displaced upward, becoming ever so slightly less weighty. And unless you've figured the weight of the log to be ten pounds at precisely the altitude it will assume in the aquarium, it will be very slightly more or less than ten pounds where it ends up.
Of course, using pound to express weight can be misleading. Pound can be a measure of mass or a measure of force. When you use a scale, you are measuring mass, and it is meaningful only if you calibrate the scale locally.
You are just looking for a friendly discussion that is going to span many pages, aren't you?
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