Steel floating in mercury problem

In summary, the conversation discusses a problem in which a steel cylinder is floating in mercury and the question asks for the length of steel that is above the surface. The equation used is vsub/vobj=(ro)obj/(ro)liquid and the correct answer is found by subtracting the length submerged from the original length. The conversation also mentions possible rounding errors and a conceptual mistake made by the student.
  • #1
Liketothink
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0

Homework Statement


A 17.85 cm diameter, 32.4 cm tall steel cylinder (ρsteel=7900 kg/m3) floats in mercury. The axis of the cylinder is perpendicular to the surface. What length of steel is above the surface?


Homework Equations


vsub/vobj=(ro)obj/(ro)liquid


The Attempt at a Solution

A
I canceled the two areas so the equation is d/h=(ro)obj/(ro)liquid and then I solved for d. H equals to 32.4 cm I think. I don't know what I'm doing wrong. Please help. Thank you.
 
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  • #2
What makes you think you're doing anything wrong? What was your answer? Do you know what the answer is supposed to be?
 
  • #3
I'm using Loncapa for my class. I received .192 m for an answer an it says I'm wrong.
 
  • #4
I get a different answer. It's close, but you may have a rounding error. Check your math! Edit, also, what value did you use for the density of mercury?
 
  • #5
13534 kg/m^3
 
  • #6
I also tried .189 m but that was wrong as well.
 
  • #8
Pay close attention to what question you're being asked. You are being asked what length of steel is ABOVE the surface. The calculation I posted is NOT for the portion that is above the surface. If you don't know what I mean, then here's a huge hint: what do you think the sub stands for in the formula you posted, vsub/vobj?
 
  • #9
I tried that as well. The .189 m ,. But that didn't work. It's ok though thank you for your help still. The teacher must have done an error in the homework problem as he frequently does.
 
  • #10
NO! Read my latest post! You have made a conceptual mistake. But what you have to do to get from 0.189 m to the right answer is very easy. ;)
 
  • #11
Oh! Yeah that's right! It's the length submerged so I have to subtract it from the original length. Thank you so much, I appreciate it.
 
  • #12
No problem! I'm glad you got it!
 

FAQ: Steel floating in mercury problem

What is the "steel floating in mercury problem"?

The "steel floating in mercury problem" refers to the phenomenon of steel objects floating on the surface of liquid mercury, despite steel being significantly denser than mercury. This has puzzled scientists for many years and has been a topic of research and discussion in the scientific community.

Why does steel float on mercury?

Steel floats on mercury due to its low surface tension and high density. Mercury has a very low surface tension, meaning that it does not form a cohesive surface film. This allows steel objects to easily break through the surface tension and float on the surface. Additionally, steel is denser than mercury, but because of the shape and size of the steel objects, they displace a greater volume of mercury and therefore appear to float.

Is it safe to float steel on mercury?

No, it is not safe to float steel on mercury. Mercury is a toxic substance that can be harmful to human health, especially if ingested or inhaled. Additionally, steel objects may contain sharp edges that could potentially cause injury if handled improperly.

What other materials can float on mercury?

Other materials that can float on mercury include aluminum, lead, and gallium. These materials have low surface tensions and high densities, similar to steel, allowing them to break through the surface tension and float on the surface of mercury.

What practical applications does the "steel floating in mercury problem" have?

The "steel floating in mercury problem" does not have any practical applications. However, the phenomenon has been studied and used as a teaching tool in physics and chemistry classes to demonstrate concepts such as surface tension and density. It has also been used in art installations and magic tricks.

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