6a. The specific gravity of steel is 7.8, yet steel battleships can float. How can this be?
The steel boat’s inside is made up of air, which means that the average density of the boat filled with air is light compared to the density of water. The bottom of the boat is in the water, most of the boat’s weight is outside of it. So a small portion of the boat is submerged in the water when it displaces the weight of the boat.
6b. Water expands when heated. Imagine a bobber floating in a cold pond. Will that bobber float higher or lower in hot water? Assume the density of the bobber doesn’t change. Justify your answer using Archimedes’s Principle.
The bobber would float lower in the hot water than the cold water. The hot water has molecules that have more energy which makes it denser. The bobber needs to displace a weight of water that is equal to the weight of the bobble. This being said, in hot water, there is a greater density so the bobber displaces a smaller amount of water than in cold water
6c. Web Research Question: Visit this webpage for a thorough discussion of Archimedes and the crown story: http://www.math.nyu.edu/~crorres/Archimedes/Crown/CrownIntro.html This page debunks the notion that Archimedes solved the crown problem by measuring its volume by displacement. First, explain in your own words why it’s not very plausible that Archimedes could have exposed the thief by measuring the volume of the crown through water displacement. Then find at least two webpages that explain the crown story the wrong way and paste quotes from them into your answer, along with their URLs. Explain why you think this scientific myth has persisted over the years.
The reason is that there was more than likely only a small percent of gold replaced with silver. The change in the volume would be very small and would almost be unnoticeable in the water. But there are different versions. The difference between gold and silver and how leaving out how small the difference it really was/is and how long the process would be. An example would be Because there was most likely only a small percentage of gold replaced with silver, the change in volume would have been very small, and essentially unnoticeable within a tub of water. However, most versions of the story solely focus on the difference between the gold and silver, leaving out how small of a difference it really is and how long the process would be. For example, “reasoning from the fact that more water was lost in the case of the crown than in that of the mass, he detected the mixing of silver with the gold, and made the theft of the contractor perfectly clear (Cut the Knot).” Because this story illustrates the Principle on an easy-to-understand level, it is easy to explain to children (cartoon).
LINKS:
https://science.howstuffworks.com/science-vs-myth/everyday-myths/question254.htm
- This link explains why can boats made of steel float on water when a bar of steel sinks
https://physics.weber.edu/carroll/archimedes/principle.htm
- This link shows a good illustration of how Archimedes principle works and talks more about the principle.
http://www.explainthatstuff.com/how-ships-work.html
-This link talks more about how boats and ships don’t sink.
https://www.pbslearningmedia.org/resource/arct15-sci-densitylab/density-lab/#.WqaqdxPwY1I
This link provides a way to learn about density through exploration and simulations. This webpage also includes additional information, resources, and simulations.
