Name: A. E. M.
What is neutral buoyancy?
A E. -
Buoyancy is the upward force on an object suspended in a fluid - a liquid or a gas. This
force is equal to the force of gravity (i.e. weight) on the fluid which is displaced by the
object. The more dense the fluid, the greater the force of gravity on the fluid displaced,
and therefore, the greater the buoyant force on the object.
Your body experiences a buoyant force because you are in the air... a fluid. In water the
buoyant force is greater and you appear to weigh less... but likely still have some downward
force and you will sink unless you start swimming. In salt water which is more dense it is
easier to stay on top of the water. If you were to jump into a vat of the denser mercury
(please do not, it is poisonous!) you would experience so much buoyant force you would easily
To your question... neutral buoyancy is when the buoyant force is equal to the force of
gravity. The net force will not move the object up or down. Submarines try for neutral
buoyancy to make traveling up and down in water as effortless as possible.
Neutral buoyancy means that the weight of an object under water is equal to the upward buoyant
force of the water on the object. Since the magnitude of the buoyant force is equal to the
weight of the water displaced by the object, any part of the water itself is in neutral
buoyancy. A submarine under water is close to neutral buoyancy. By admitting water to their
buoyancy tanks or blowing it out, a submarine can adjust the buoyant force until it just
balances the total weight of the submarine. Fish also are
designed to be in close to neutral buoyancy. They can, in fact, sleep without rising or
Humans are also close to neutral buoyancy. When under water, I can adjust my buoyancy by
expelling air from my lungs until I just start to sink. If I expel air until I stay at the
same depth, I am in neutral buoyancy.
Best, Dick Plano...
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Update: June 2012