Problem #29 - Demonstration 2, Archimedes in my Swimming Pool

Problem #29 - Demonstration 2, Archimedes in my Swimming Pool

[xy]

Prof Lewin, this was beautiful!!! I was thinking in another possibility. In the experiment the boat itself weights and displace not only water, but also air. Considering this, if we put sulphur hexafluoride in the boat it will sink and the water level will rise. And we can continue with the experiment using our imagination and replace the sulphur hexafluoride with helium or hydrogen, without letting it escape from the boat. Then the boat should go up and the water level down. So we can have a thing in our boat that itself can float on water and make a difference in the level, taking that thing out of the boat.

[aaqidmasoodi]

"I never talk about my family members having "died" in concentration camps. I always use the word murdered, so we do not let language hide the reality" Professor Lewin! I Love You. I want to meet you someday and give you a hug. You're a Great Man! I am going to graduate school to learn Physics and Mathematics. I love both of these subjects EQUALLY Wish me Best!

[ximalas]

This is not a primitive demonstration, it conveys the points beautifully.

[billholmes]

An awsome and very clear explanation as per usual!

[dionchaney]

Thank you again for all of your time and effort in thought and demonstrations. But wouldn't the value of the line change if the rock was made of lead or something much lighter like aluminum?

[esa]

Walter Lewin demonstrations, always delightfully simple and clarifying. Aren't we lucky :-)

[nigarabbasova]

Thank you Professor! Still loving Physics and definitely continuing being friends with you! Thank you! :)

[Abhisruta]

I saw you handing pen many days after, I much like your hands of knowledge...

[jean-pierrejrrichard]

Good Morning from Haiti to you Sir,

You have no idea of what a blessing your YouTube channel is for individuals like myself specially since I'm living in "apparently" such a poor country like Haiti. After I watch your demo here it gives me a better understanding of what the Archimedes notion is really about.
Now I'm tempted to ask this: If all the Antarctica iceberg come to melt sea level will not rise as we might be tempted to think right (I'm referring to the new climate trend depicted by the media outlets just to understand what this is all about)?

Again, I wish you all the best and specially to remain healthy for your work is University touching lives in a good way. God bless you always!

[fabienchapuis]

what when the iron will melt? will take a little more than 20 min if i'm right.

[corwinchristensen]

Professor Lewin, I posed this question to my high school age children and they were able to answer surprisingly well. However, when I talked about the rock in the boat and then in the pool, I had a NaCl crystal that I picked up (I tend to use props when I talk) and the question came up - what happens to the water level when the salt crystal changes to solution? The first part is easy, assuming the quantity of salt is sufficient in relation to the volume of water, the density of the water will increase so the boat will displace less volume and the water level will go down. BUT .. how does the transformation of the salt into solution affect the level in the pool? If the boat is removed from the system and you place a large salt crystal in the "pool", how would the water level react to the change of the NaCl from crystal to solution? I tried Google and I haven't had any success and I don't want to ruin my crystal to perform an experiment (looking for another large crystal to experiment with.) I think my issue is that I don't know exactly how to word my question. Can you suggest where to get an answer to this question, or even better answer it yourself? Thanks for the lectures/videos and thanks in advance for your reply.

[manishprasad]

So there are only three things that we need to think about in this question...

If the obj floats then it doesn't matter if it is in the boat or out of the boat and the water level remains constant

If obj sinks, water level goes down when it is thrown in the water..

If it is ice water level still doesnt change...

Is this correct ??

[alwysrite]

might be primitive but it will stay in my mind forever! just like your other videos (I never forget the rainbow one)

[foxtrottNB]

What happens if there is a boat swimming inside another boat and you do the same experiment from the inner boat to the outer boat?

[abbaskhan]

Professor! please answer my question
Resistance of electrons cannot be equal to zero which means voltage/current are always greater than zero, Electrons are always continuous in motion since the beginning of the universe ?But, what About this motion before bigbang?, i failed to imagine this.
Thanks.

[iOSMinecraft]

The reason why the water level goes down when the object inside the boat is heavier is that: when it is inside, the object pulls down the boat more and causes more air to displace the water while inside the boat; but when it is outside the boat, it will simply sink and the air from the previous case does not displace the water any more, and so the water level sinks. Is that correct?

[europaeuropa]

I still think the ice below the surface contributes to a very slight level decrease(after it melts) due to the volume of submerged ice being greater than the volume of water from the submerged ice that has melted.

[iftik]

Sir, instead of rock or ice if we use some object that floats partially on water for this experiment then what will happen?

[chinnasaiprathapmeesala]

please any one explain why level of water is fall after placing the rocks into water

[Mrsrk]

In short we can say that, the total density of boat varies with rock inside it and removed from boat.... Level of water completly depends on the relative density of material placed in