Archimedes Principle Kit

Quick Answer: The Archimedes Principle Kit is a practical set for verifying that the upthrust on an immersed object equals the weight of the liquid it displaces. The listing image shows a retort stand holding a spring balance and a metal sinker, a glass overflow can, and a beaker that collects the displaced liquid.

Specifications

Measuring Upthrust and Displaced Liquid

Archimedes’ principle states that a body wholly or partly immersed in a fluid experiences an upward force equal to the weight of fluid it pushes aside. In this kit the spring balance first reads the sinker’s weight in air. When the sinker is lowered into the overflow can, the balance reading falls, and that loss of weight is the upthrust.

The overflow can, sometimes called a eureka can, is filled until water just runs out of its spout and then left to stop dripping. Any liquid leaving the spout after the sinker goes in has been displaced by it and runs into the catch beaker. Weighing that liquid, or measuring its volume in a measuring cylinder, gives the second number, and in a careful experiment the two agree closely.

Because the readings are simple, the Archimedes principle kit also supports calculations of relative density: weight in air divided by loss of weight in water. Repeating with salt water or another liquid shows that denser liquids give more upthrust for the same object. Vessel capacities and the balance range should be confirmed when ordering.

Applications

• Verifying Archimedes’ principle as a standard practical in secondary physics
• Finding the relative density of a solid from its weight in air and in water
• Comparing upthrust in fresh water and salt water to explain why ships float higher at sea
• Introducing flotation, hydrometers and how submarines dive and surface

Care & Handling

• Level the stand and let the sinker hang freely, clear of the can walls, before reading the balance.
• Wait for the overflow can to stop dripping before each trial, otherwise extra liquid will be counted as displaced.
• Dry the sinker and the balance hook after use so they do not corrode.
• Handle the glass can and beaker by the body, not the spout, and store them where they cannot roll.

Why Choose LabEquip

Physics teachers preparing students for practical assessments choose this set because every quantity in Archimedes’ principle is measured directly. LabEquip lists the kit in its STEM kits range, and the Archimedes Principle Screw Model is available for lessons on the separate water-lifting invention that also carries his name. Use the contact page to discuss class quantities.

Frequently Asked Questions

Why does the object weigh less when it is in water?

The water pushes up on the object with a force called upthrust or buoyant force. The spring balance now supports only the difference between the object’s weight and that upward push, so the reading falls. The object’s mass has not changed.

Why must the overflow can be filled until it drips?

The can must start exactly full to the spout. Only then does every drop that leaves the spout after the object goes in represent displaced water. If the level starts below the spout, the first displaced water just raises the level and never reaches the beaker.

Does the material of the object affect the upthrust?

For a fully immersed object, no. Upthrust depends only on the volume of liquid displaced and the density of that liquid. An aluminium block and a lead block of equal volume receive the same upthrust, although the lead one is much heavier.

How do I calculate relative density with this kit?

Divide the object’s weight in air by its loss of weight when fully immersed in water. Because the loss of weight equals the weight of an equal volume of water, the ratio compares the density of the object with that of water.

What if the liquid is salt water instead of fresh water?

Salt water is denser, so the same volume displaced weighs more and the upthrust is larger. The balance reading drops further than in fresh water. This is why a ship floats slightly higher in the sea than in a river.

What are the main sources of error?

Drips clinging to the spout or the beaker, the sinker touching the side of the can, air bubbles on the sinker and reading the spring balance at an angle all affect the result. Tapping the spout gently and taking readings at eye level reduce these errors.

Last Updated: September 2026