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


              94
                                                                         Student’s Book Form One



     Physics Form 1 Final.indd   94                                                         16/10/2024   20:56
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