Page 100 - Physics
P. 100
Physics for Secondary Schools
Chapter Five
Sinking and fl oating
Introducti on
Sinking and fl oating is a fundamental phenomenon with practical applications
in a wide range of fi elds, including ship building, marine engineering, and even
understanding the behaviour of gases in the atmosphere. Archimedes’ principle
and the law of fl oatation are important laws of physics that explain the nature and
mechanism of sinking and fl oating. Understanding these concepts is essential
for designing stable and buoyant structures that can navigate fl uid environments
effectively. In this chapter, the concept of sinking and fl oating, Archimedes’ principle
and the law of fl oatation will be discussed. Competencies developed will enable you
to effi ciently use the phenomenon of fl oating and sinking in your daily activities.
Think
objects which are naturally sink but can be molded to make them fl oat
Concept of sinking and fl oating the upthrust acting on the bottle.
When an object is placed in water, it either sinks Therefore, fl oating is the tendency
(goes down into the water) or fl oats (stays on of an object suspended in water to
the surface of the water). Figure 5.1 (a) shows stay on the surface of the water.
a sealed empty plastic bottle fl oats on water On the other hand, sinking is the
because its weight is less than the upthrust tendency of an object to go to the
exerted on it by water. lower level of water.
Empty bottle Bottle fi lled with sand Whether an object fl oats or sinks in
a fl uid depends on its relative size,
weight, and the upthrust acting
on the object. If the weight of the
object is greater than the upthrust,
(a) Empty bottle (b) Bottle fi lled with the object moves downward and
fl oating on water sand sinks in water
therefore sinks. If the weight of an
Figure 5.1: Sinking and fl oating object is less than the upthrust, the
While the sand-fi lled bottle shown in Figure object will stay on the surface of
5.1 (b) sinks because its weight is larger than the fl uid and therefore fl oat. The
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Student’s Book Form One
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