7TH GRADE · ARCHIMEDES' STRENGTH AND SWIMMING
Floating bodies, ships and balloons
Descent, ascent, balance and average density.
The entire theory of the lesson is collected here; you can read it without an account. In interactive mode, the same theory appears as cards, followed by questions. with checking the answer and task, and progress is saved.
Basic Concepts
Sailing condition
A floating body is in equilibrium when the buoyant force is equal in magnitude to the force of gravity.
If the average density of a body is less than the density of the liquid, it floats up and sinks only partially.
Diving and ascent
A body sinks when gravity predominates and floats when buoyant force predominates.
By changing the average ballast density or the volume of the gas shell, underwater vehicles and balloons are controlled.
Ships and aeronautics
Hollow vessels and balloons use a large displacement volume to obtain the required buoyant force.
The steel ship floats on the water thanks to the low average density of the hull with air, and the ball rises in the atmosphere.
Physical quantities
Average body density
The ratio of total body mass to its external volume.
Unit: kilogram per cubic meter ·
Lesson formulas
Equilibrium of a floating body
During calm swimming, the buoyant force is equal to the force of gravity.
Related formulas
The same formulas in the reference, with symbols and units.
Tasks on the topic
Statements, answer options and the walkthrough.