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Testing a Gold Crown with Water — Archimedes' Buoyancy and the Eureka Method
King Hiero of Syracuse suspected his goldsmith had cut his crown with cheaper silver, but how do you check without melting it down? Around 250 BC Archimedes solved it in the bath: stepping in, he saw the water rise by his own volume and realised a submerged object displaces its own volume of water. Density — weight divided by volume — then betrays any cheating, because gold is far denser than silver. This blueprint reproduces both the famous displacement test and Archimedes' more precise underwater-balance method, and states the buoyancy principle that floats every ship.
Pertengahan
2
Arahan
1
1
Understand the problem
Understand the problem
You must find whether a crown is pure gold without damaging it. The key is density — weight divided by volume. Pure gold is very dense (about 19.3 g/cm³); gold mixed with lighter silver (about 10.5 g/cm³) is less dense, so the same weight of it takes up more space.
2
2
The Eureka insight
The Eureka insight
When a solid is lowered into water it pushes aside — displaces — exactly its own volume of water. So even an oddly shaped crown's volume can be measured by how much water it displaces. This is what Archimedes realised watching the bath overflow.
3
3
Set up an equal-arm balance
Set up an equal-arm balance
Hang a balance scale, or make an equal-arm balance from a rod and string with a small pan on each end, so it swings level and can compare two weights precisely.
Alatan diperlukan:
Neraca dua piring4
4
Balance the crown against pure gold in air
Balance the crown against pure gold in air
On the balance, set the crown against an equal weight of known pure gold, in air, until the two sides hang exactly level. Now they weigh the same — the only question left is whether they take up the same volume.
Bahan untuk langkah ini:
Jongkong Plumbum1 kepingAlatan diperlukan:
Neraca dua piring5
5
Submerge both in water
Submerge both in water
Lower both objects, still on the balance, into a vessel of water. Each is pushed up by a buoyant force equal to the weight of the water it displaces — the bulkier object is pushed up harder.
Bahan untuk langkah ini:
Air5 literAlatan diperlukan:
Balang Kaca Bertutup
Tali Kapas Dapur6
6
Read the verdict
Read the verdict
If the crown is pure gold it has the same volume as the gold and the balance stays level under water. If it is adulterated with lighter silver it is bulkier, displaces more water, is buoyed up more, and its side rises — proof the crown is not pure gold.
Alatan diperlukan:
Neraca dua piring7
7
Or measure density directly
Or measure density directly
The simpler displacement version: weigh the crown, then submerge it in a brim-full vessel and measure the overflow — that volume is the crown's volume. Density = weight ÷ volume. Compare to pure gold's 19.3 g/cm³; an adulterated crown reads lower.
Alatan diperlukan:
Balang Kaca Bertutup8
8
State Archimedes' principle
State Archimedes' principle
Any body in a fluid is pushed up by a force equal to the weight of the fluid it displaces. That single law tells the crown from a fake, floats a loaded ship, and lifts a balloon — one of the oldest exact laws of physics, from around 250 BC.
Bahan
4- 1 kepingPemegang Tempat
- 5 literPemegang Tempat
- 1 kepingPemegang Tempat
- 1 kepingPemegang Tempat
Alatan Diperlukan
3- Pemegang Tempat
- Pemegang Tempat
- Pemegang Tempat
Blueprint berkaitan
Blueprint ini berkongsi pengetahuan — teknik, bahan atau prinsip
CC0 Domain Awam
Blueprint ini dikeluarkan di bawah CC0. Anda bebas menyalin, mengubah, mengedar, dan menggunakan karya ini untuk sebarang tujuan, tanpa meminta kebenaran.
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