What's a ton of CO2?

[FatBaldGuy]

Now, if you froze the CO2 and put the dry ice on your scale…

[mangeorge]

@FatBaldGuy

Now, if you froze the CO2 and put the dry ice on your scale…

I was going to say that, but I was afraid everybody would (again) laugh at me.

[Exapno_Mapcase]

@Xema

If what’s in the balloon is helium or hydrogen, it will not lie flat against a scale.

Remember the part about “Special circumstances” that you actually quoted?

Why would a balloon resting on a scale see buoyancy effects different from if it were dangling? The buoyance is due to the surrounding atmosphere - it has nothing to do with how the balloon is supported.

Buoyancy is not magical. It’s a simple description of outside pressure against an object.It has everything to do with how the object is supported. Putting an object onto a scale cuts off the majority of that pressure. Putting an object at the bottom of a lake cuts off the buoyancy of the water. There remain some side effects - literally against the sides - but obviously a floating object behaves differently than an object resting against a surface.

[robby]

@Exapno_Mapcase

Putting an object onto a scale cuts off the majority of that pressure. Putting an object at the bottom of a lake cuts off the buoyancy of the water. There remain some side effects - literally against the sides - but obviously a floating object behaves differently than an object resting against a surface.

This is completely incorrect. Buoyancy is not affected by whether or not an object is resting on a surface (such as a lake bed).

A submerged object experiences the same buoyant force whether it on resting on the bottom or not. The buoyant force is equal to the weight of fluid displaced. Period.

[Santo_Rugger]

@Exapno_Mapcase

Remember the part about “Special circumstances” that you actually quoted?
Buoyancy is not magical. It’s a simple description of outside pressure against an object.It has everything to do with how the object is supported. Putting an object onto a scale cuts off the majority of that pressure. Putting an object at the bottom of a lake cuts off the buoyancy of the water. There remain some side effects - literally against the sides - but obviously a floating object behaves differently than an object resting against a surface.

Where are you getting your ideas from? A floating object displaces it’s weight; a submersed object displacees it’s volume. The weight of fluid displaced is the upward force exerted on the object. It has nothing to do with how the object is supported. Try this simple experiment. Take a cup, turn it upside down, and lower it into a full sink until it’s at the very bottom. Even though the cup is touching the bottom of the sink when you let go of it, it’s going to shoot straight up. A floating object behaves differently than a submerged object, but an object submerged 10 inches displays (roughly) the same buoyancy effects as an object submerged by 10 miles, regardless if it’s resting on anything (not taking into account the compressibility effects of the water).

Buoyancy

Specifically:

Buoyancy |

Vitruvius (De architectura IX.9–12) recounts the famous story of Archimedes making this discovery while in the bath. He was given the task of finding out if a goldsmith, who worked for the king, was carefully replacing the king’s gold with silver. While doing this Archimedes decided he should take a break so went to take a bath. While entering the bath he noticed that when he placed his legs in, water spilled over the edge. Struck by a moment of realisation, he shouted “Eureka!” He informed the king that there was a way to positively tell if the smith was cheating him. Knowing that gold has a higher density than silver, he placed the king’s crown and a gold crown of equal weight into a pool. Since the king’s crown caused more water to overflow, it was, therefore, less dense, Archimedes concluded that it contained silver, causing the smith to be executed. The actual record of Archimedes’ discoveries appears in his two-volume work, On Floating Bodies. The ancient Chinese child prodigy Cao Chong also applied the principle of buoyancy in order to accurately weigh an elephant, as described in the Sanguo Zhi.

The weight of the displaced fluid is directly proportional to the volume of the displaced fluid (if the surrounding fluid is of uniform density). Thus, among completely submerged objects with equal masses, objects with greater volume have greater buoyancy.

[Xema]

@Exapno_Mapcase

Putting an object at the bottom of a lake cuts off the buoyancy of the water.

This argues that if you put an ice cube in an empty cup which you then fill with water, the ice cube won’t float. I can assure you it ain’t so.