Page 103 - Physics

Sinking and fl oating

The rising of the cork shows that, while Scuba diving; divers use buoyancy
inside the liquid, an upward force acts on control devices (BCDs) to achieve neutral
it. Since this force is greater than the weight buoyancy, allowing them to hover at a
of the cork, it is pushed up to the surface desired depth without sinking or fl oating
of the liquid. An upward force acting on an to the surface.
object that is totally or partially immersed
in a fl uid is called an upthrust or buoyant Underwater research and engineering;
force. Upthrust enables an object to fl oat neutral buoyancy is employed in
or feel lighter in a fl uid. underwater laboratories and simulators to
conduct experiments and train astronauts
When one is swims in water, his or her for spacewalks (extravehicular activities

weight is balanced by the upthrust acting or EVAs) as the microgravity conditions
on the body. Water vessels, like ships and in space are similar to those of neutral
boats, fl oat and sail on water due to this buoyancy.
force, otherwise, they would sink. The
tendency or ability of an object to fl oat on a Marine biology; researchers and divers
fl uid suspended on it is called buoyancy and use neutral buoyancy to study marine life
the upward force exerted by a fl uid on that without disturbing the natural environment.
object is called upthrust (buoyant force).
Buoyancy is the force that determines Apparent weight of an object
whether an object will sink, fl oat, or remain If one attempts to lift an object in a
suspended in a fl uid. This concepts was best swimming pool and then, attempts to lift
described by Archimedes, who famously the same object outside of the pool, it feels
shouted “Eureka!” when he discovered the much lighter in the pool than when outside.
phenomenon. This is the effect of upthrust. When a body
is totally or partially immersed in a fl uid,

In addition, an object is said to experience it experiences an upthrust exerted by the
neutral buoyancy when its average density fl uid. The upthrust is equal to the weight
is equal to the density of the surrounding of the fl uid displaced by the immersed
object. Because of upthrust, an object that is
fl uid. In this state, the buoyant force is submerged in the fl uid appears to weigh less
precisely equal to the gravitational force than its actual weight in air. The weight of
acting on the object, resulting in a net the submerged object is known as apparent
force of zero. As a consequence, the object weight, while its weight in air is referred
remains suspended at a specifi c depth in to as the actual weight. The difference
the fl uid without any vertical acceleration. between the weight and the apparent weight

Neutral buoyancy is particularly important of an object is referred to as the apparent
in various fi elds, including: loss in weight.

97

Physics Form 1 Final.indd 97 16/10/2024 20:56