Fluids
Float in water
Watch the light cork bob up — buoyancy balances weight when enough volume is submerged.
Investigate buoyancy and Archimedes' principle by placing objects in a fluid zone. Watch floating and sinking behavior with live buoyant force and displaced volume readings.
Buoyancy
An object floats when the upward buoyant force equals its weight. The submerged volume adjusts until equilibrium.
Archimedes' principle: the buoyant force equals the weight of displaced fluid. A light cork rises until enough volume is underwater to support its weight.
- F_b = ρ_fluid · V_sub · g
- Float: F_b = mg
Investigation brief
Plan the question before you open the lab
The brief mirrors the prerendered page: driving question, competing predictions, variable roles, governing laws, setup, analysis and extension prompts remain visible and in this order.
Driving question
A cork floats in water. If you use a heavier cork of the same size, how will the buoyant force holding it up change?
Predictions to weigh
- The buoyant force increases to match the heavier weight.
- The buoyant force stays the same no matter the mass.
- The buoyant force decreases because the cork sits lower.
Variable roles
What you set:
- Cork mass m (kg)
What you measure:
- Submerged fraction
- Buoyant force F_b (N)
How the investigation runs
- Open the fluid-float preset and press Reset. A cork floats at the water's surface.
- Enable the buoyant-force probe on the cork.
- Set the cork's mass for each trial, let it settle to equilibrium, and record the submerged fraction and the buoyant-force reading.
Governing equation
Archimedes' Principle — F_b = ρ·V·g
The buoyant force on a submerged (or floating) object equals the weight of fluid it displaces. At equilibrium, a floating object's buoyant force exactly balances its weight — that's why your two columns should match.
What the printable worksheet asks students to work out
- For each trial, compute m·g using g = 9.8 m/s² and compare it to the buoyant-force reading.
- Explain why a floating object's buoyant force always equals its weight, regardless of how much of it is submerged.
Where this shows up beyond the lab
- If you kept adding mass to the cork, at what point would it stop floating and sink instead? What would have to be true about the buoyant force at that point?
- A steel block sinks, but a steel ship floats. Using Archimedes' principle, explain how shape — not material — makes this possible.
- AP Physics 1 — Unit 8: Fluids
- General High School Physics — Fluids & pressure
- NGSS High School Physics — Forces and Newton's second law
- Which is bigger?
- Raise the mass
- Capture the float
- Open the data
- Explain your evidence
Open the interactive simulation to build the scene, press Play, and explore with live measurements and a guided tutorial.