Solving Archimedes' Problem: Is the Crown Gold?

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In summary, the crown is made of lead and gold, and it is not solid gold. The density of lead is greater than the density of gold, so the crown is mostly lead.
  • #1
tandoorichicken
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A king's crown is said to be solid gold but may be made of lead and covered with gold. When it is weighed in air, the scale reads .475 kg. When it is submerged in water, the scale reads .437 kg. (a) is it solid gold? (b) if not, what percentage by mass is gold?

density of gold = 19.3 * 10^3 kg/m^3
density of lead = 11.4 * 10^3 kg/m^3
 
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  • #2
Originally posted by tandoorichicken
A king's crown is said to be solid gold but may be made of lead and covered with gold. When it is weighed in air, the scale reads .475 kg. When it is submerged in water, the scale reads .437 kg. (a) is it solid gold? (b) if not, what percentage by mass is gold?

density of gold = 19.3 * 10^3 kg/m^3
density of lead = 11.4 * 10^3 kg/m^3

I'll do units in g/cm

mass in water:
m = pv (crown) - pv (water)
0.437 = pv - 1v
0.437 = (p - 1)v
v = 0.437/(p - 1)

mass in air:
m = pv
0.475 = p(0.437/(p - 1))
0.475 = 0.437p/(p - 1)
0.475p - 0.475 = 0.437p
0.038p = 0.475
p = 12.5

So it's not gold.

density composition, x is the amount of gold
p = 19.3x + 11.4(1 - x)
12.5 = 19.3x + 11.4 - 11.4x
1.1 = 7.9x
x = 0.1392

The crown is roughly 14% gold and 86% lead.
 
  • #3
ShawnD- Don't go doing all of TandooriChicken's homework for him! Make him show that he has at least attempted the problem himself!
 
  • #4
Ok I won't do that next time.
Think of it this way though, if tandoori went through the trouble of posting it here, he is probably serious about wanting to know the answer. Most teachers don't even mark you based on your homework; in all of my high school math, chem, physics and biology classes, homework was never checked or marked.

IIRC, tandoori said he was homeschooled. His instructor is (most likely) not university educated or even familiar with doing slightly difficult math procedures such as making that equation to find the percentages of each element.
 
  • #5
homeschooled? don't remember ever saying that...
hmmm maybe you were talking wit a different tandoori shawnd.
anyways, thanks for the help.
and yeah, most of the problems i post here i either don't know how to start or got lost halfway through. I am no slacker hehe :-p
 
  • #6
shawnd, are you sure that the second part is mass percent? because your post says density comp.
 
  • #7
I misread the question, I'm sure you can figure that out with all the info given and solved for.
 

1. What was Archimedes' problem and why is it significant?

Archimedes' problem was to determine whether a crown given to him by the king was made entirely of gold, or if it contained some other metal. This problem is significant because it showcases Archimedes' brilliant use of geometric principles to solve a real-world problem, and also demonstrates the importance of accurate measurement and the concept of density.

2. How did Archimedes solve the problem?

Archimedes used his famous "Eureka!" moment to solve the problem. He realized that he could determine the volume of the crown by measuring the amount of water it displaced when submerged. He then compared this volume to the volume of a solid gold object with the same weight. If the volume of the crown was larger, it meant that it contained some other metal with a lower density.

3. Did Archimedes' method work?

Yes, Archimedes' method worked. He discovered that the crown was indeed not made entirely of gold, as it had a lower density than pure gold. He was able to determine the exact amount of gold and other metals in the crown by using his method.

4. What was the significance of Archimedes' solution?

Archimedes' solution to this problem was significant because it was a breakthrough in the understanding of density and how it can be used to determine the purity of a substance. It also demonstrated the power and practical applications of mathematics in real-world problems.

5. How has Archimedes' solution influenced modern science?

Archimedes' solution has had a significant impact on modern science, especially in the field of physics. His principle of displacement and his method for determining density have been used in various experiments and calculations. His problem-solving approach and innovative thinking have also influenced scientists and mathematicians throughout history.

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