Best examples of Archimedes' principle experiment you can actually do

When people ask for examples of Archimedes’ principle experiment, this is usually where they begin: a clear container of water, a set of objects with different densities, and a way to measure forces.

Fill a deep container with water and gather objects such as:

• A metal bolt
• A plastic spoon
• A small block of wood
• A sealed glass jar partially filled with sand

First, weigh each object in air using a spring scale. Then lower each object into the water while it’s still attached to the scale. The reading on the scale drops because the water exerts an upward buoyant force. The difference between the weight in air and the apparent weight in water equals the buoyant force, which, according to Archimedes’ principle, equals the weight of the displaced water.

This very basic setup is one of the best examples of Archimedes’ principle experiment for beginners because it visibly connects three things:

• Volume of the submerged part of the object
• Weight of displaced water
• Change in the scale reading (buoyant force)

You can extend this example of an experiment by switching from water to saltwater and comparing the results. As density increases, the same volume of displaced fluid weighs more, so the buoyant force increases.

Aluminum foil boats: everyday engineering with Archimedes’ principle

If you want examples of Archimedes’ principle experiment that feel like engineering rather than just physics, aluminum foil boats are perfect.

Take identical sheets of aluminum foil and shape them into different boat designs: a shallow tray, a deep narrow hull, a sphere, and a crumpled ball. Float each one in water and slowly add small weights (coins, metal nuts, or washers) until the boat sinks.

Here’s what students see in this example of Archimedes’ principle experiment:

• Designs that spread out the hull increase the volume of water displaced before the rim dips under.
• The more water displaced, the greater the buoyant force.
• The maximum load before sinking directly reflects how much weight the displaced water can support.

This is not just a classroom trick. Ship and barge design uses the same principle, scaled up and refined with computational tools. Naval architecture programs, such as those at the U.S. Naval Academy and MIT, teach design rules that ultimately tie back to Archimedes’ idea that the buoyant force equals the weight of displaced fluid.

For background on buoyancy and density, the University of Colorado Boulder PhET simulations (https://phet.colorado.edu) provide interactive tools that mirror what you see in this experiment.

Measuring density with a spring scale: a quantitative example of Archimedes’ principle experiment

Once students grasp the basic idea, you can move to one of the best quantitative examples of Archimedes’ principle experiment: measuring the density of irregular objects.

You need:

• A spring scale
• A beaker of water deep enough to fully submerge the object
• An irregular solid (a rock, a metal figurine, a wrench)

Steps:

• Measure the weight of the object in air using the spring scale.
• Submerge the object completely in water without it touching the bottom or sides. Record the new, lower reading.
• The difference between the two readings is the buoyant force.

Because the buoyant force equals the weight of displaced water, you can compute the volume of the object:

\[ V_{object} = \frac{F_{buoyant}}{\rho_{water} g} \]

Then density is:

\[ \rho_{object} = \frac{W_{air}/g}{V_{object}} \]

This example of Archimedes’ principle experiment mirrors industrial methods used to test material density when direct volume measurements are awkward. The same logic underpins hydrostatic weighing techniques used in body composition labs, where a person’s density is estimated by comparing their weight in air and water. The National Institutes of Health (NIH) has published research using similar density-based methods for body composition analysis: https://www.ncbi.nlm.nih.gov.

Overflow can and displaced water: a classic lab demonstration

Another classic in any list of examples of Archimedes’ principle experiment uses an overflow can or a container with a side spout.

Set up:

• Fill the overflow can to the brim so water just begins to drip out of the side spout.
• Place a catch container under the spout.
• Gently lower a solid object into the can until it is fully submerged.

Water will spill out into the catch container. Weigh the collected water and compare its weight to the buoyant force measured with a spring scale (weigh the object in air and then while submerged). In a well-run experiment, the weight of the displaced water matches the buoyant force within experimental uncertainty.

This example of an experiment is powerful because it makes the phrase “weight of displaced fluid” literal and visible. The mass of spilled water is not an abstract idea—it’s right there in a beaker on the balance.

Cartesian diver: a dynamic, pressure-based example of Archimedes’ principle

The Cartesian diver is one of the most famous examples of Archimedes’ principle experiment that also introduces pressure and compressibility.

You need:

• A clear plastic bottle with a tight cap
• Water
• A “diver” (a small eyedropper, pipette, or ketchup packet that just barely floats)

Fill the bottle with water and place the diver inside. When you squeeze the bottle, the pressure increases, compressing the air inside the diver. Its volume decreases slightly, its average density increases, and it sinks. Release the pressure and it rises again.

Even though this looks like magic, it’s still an example of Archimedes’ principle experiment:

• When the diver’s volume decreases, it displaces less water.
• Less displaced water means a smaller buoyant force.
• If the diver’s weight now exceeds the buoyant force, it sinks.

This experiment nicely connects Archimedes’ principle to fluid statics and gas laws, which are core topics in undergraduate physics and engineering curricula at universities such as Harvard and Stanford.

Hot air balloons and weather balloons: large-scale real examples

If you want real examples of Archimedes’ principle outside the lab, look up—literally. Hot air balloons and weather balloons are large-scale examples of Archimedes’ principle experiment playing out in the atmosphere.

For a classroom-scale model, you can:

• Use a lightweight plastic bag or thin trash bag.
• Fill it with warm air from a safe heat source (such as a hair dryer on low setting, supervised and used carefully).
• Seal the opening and observe whether the bag rises or at least becomes “lighter” when suspended from a scale.

In the real world, meteorological agencies like the National Weather Service (https://www.weather.gov) launch helium-filled weather balloons that rise until the buoyant force balances the weight of the balloon system and the changing density of air. The physics is the same as in any example of Archimedes’ principle experiment:

• The balloon displaces a volume of air.
• The weight of that displaced air is the buoyant force.
• If the buoyant force exceeds the balloon’s weight, it accelerates upward.

These real examples connect classroom buoyancy to climate modeling, storm tracking, and long-term atmospheric research.

Submarines and ballast tanks: controlled buoyancy as a working example

Submarines and research submersibles provide some of the best examples of Archimedes’ principle experiment being used for precise control. Instead of passively floating or sinking, they actively manage buoyancy.

You can model this in a lab using:

• A sealed plastic bottle with small holes near the bottom
• A removable cap
• Weights taped to the outside

When the bottle is empty of water and sealed, it floats. Open the cap and let water enter through the holes; as water fills the bottle, its average density increases. At a certain point, the weight of the bottle-plus-water exceeds the buoyant force, and it sinks. Letting water drain out or replacing it with air reverses the process.

Real submarines do the same thing with ballast tanks. Navy and oceanographic fleets, including those overseen by the U.S. Navy and research institutions like Woods Hole Oceanographic Institution, rely on Archimedes’ principle for safe diving and surfacing. These are not just thought experiments; they are real examples that determine whether multi-million-dollar vessels operate safely.

Hydrometers and battery testers: practical measuring devices

Hydrometers are simple instruments that float in a liquid to measure its density. They are another practical example of Archimedes’ principle experiment embedded in everyday tools.

To build a basic hydrometer:

• Take a thin plastic straw.
• Seal one end with wax or tape.
• Add small weights (sand or metal shot) until it floats upright in water.
• Mark the water level on the straw.

Now place the hydrometer in saltwater, sugar solution, or other liquids. The straw will float higher in denser liquids and lower in less dense liquids. You can calibrate the scale using known concentrations.

This is one of the best examples of Archimedes’ principle experiment for showing how industry measures things like:

• Battery electrolyte strength in automotive maintenance
• Sugar content in juices and wines
• Salinity of seawater in oceanography

Hydrometers appear in engineering and environmental science labs throughout universities and agencies such as the U.S. Geological Survey (USGS), where fluid density measurements matter for water quality and sediment studies.

Modern research and 2024–2025 trends using Archimedes’ principle

Even in 2024–2025, Archimedes’ principle is not “old news.” Many modern technologies and research methods still rely on the same physics as the classroom examples of Archimedes’ principle experiment.

Some current directions include:

• Microfluidics and lab-on-a-chip devices: Researchers use buoyancy differences to separate cells, droplets, and particles in tiny fluid channels. The same force balance you see in a beaker experiment now operates at the micrometer scale.
• Advanced materials and foams: Engineers design ultra-light foams and metamaterials whose behavior in fluids is tested by measuring buoyant forces and displaced volume. These tests are basically refined examples of Archimedes’ principle experiment.
• Buoyant energy storage: Some renewable energy concepts store energy by using heavy weights on the seafloor and buoyant structures that rise and sink in water columns, a direct application of buoyancy and displaced volume.

Educational resources from institutions like MIT OpenCourseWare (https://ocw.mit.edu) and Khan Academy (https://www.khanacademy.org) continue to feature Archimedes’ principle in updated physics and engineering courses, showing that the same ideas behind your foil boat or overflow can are still part of current science and technology.

FAQ: common questions about examples of Archimedes’ principle experiment

What are some simple classroom examples of Archimedes’ principle experiment?

Simple classroom examples include sink-or-float tests with a spring scale, aluminum foil boats loaded with coins, and overflow can demonstrations where displaced water is collected and weighed. Each example of a setup highlights the connection between displaced volume and buoyant force.

Can you give an example of Archimedes’ principle used in real life?

Hot air balloons, weather balloons, and ships are real examples that rely on Archimedes’ principle every day. Submarines and diving bells adjust their buoyancy by changing how much water they take into ballast tanks, which is essentially a controlled, large-scale example of Archimedes’ principle experiment.

How do hydrometers show Archimedes’ principle in action?

Hydrometers float at different depths depending on the liquid’s density. The instrument sinks until the weight of the displaced liquid equals the weight of the hydrometer. This is a direct, repeatable example of Archimedes’ principle experiment applied to measuring density in industries like winemaking, battery maintenance, and environmental monitoring.

Are there advanced or modern examples of Archimedes’ principle experiment in research?

Yes. Microfluidic devices that sort cells by density, hydrostatic weighing for body composition in sports science and medicine, and buoyancy-based separation techniques in chemical engineering all build on the same principle. These are more sophisticated examples of Archimedes’ principle experiment, but the core idea—buoyant force equals the weight of displaced fluid—has not changed.

How can I design the best examples of Archimedes’ principle experiment for a science fair?

Combine visual impact with measurable data. A strong project might pair aluminum foil boat designs with precise load measurements, or compare the buoyant behavior of objects in water vs. saltwater. Include clear graphs of displaced volume, weight, and buoyant force, and explain how your results fit the theory. Judges respond well to real examples where the data clearly backs up the physics.