Page 109 - Physics

Sinking and fl oating

4. A body lost 0.6 N in weight when then,
immersed in water. Calculate its mass of substance
volume in cubic centimetres. volume of substance
5. State Archimedes’ principle and state R.D = mass of water
its application in daily life. volume of water
6. Design an activity to verify
Archimedes’ principle in the home If the volume of a substance is equal to
environment. the volume of water, then
7. Assume a body weighs X N in the air mass of substance
and experiences an upthrust of Y N R.D = mass of equal volume of water
in a liquid. Write the expression for
apparent weight in terms of X and Y. Since,
8. Why does a stone weigh more in air weight in air = mass of asubstance ×
than when immersed in water?
acceleration due to graviy

Determination of relative density
using the Archimedes’ principle Then,
weight of substance in air
In Chapter Four, you learnt the concept R.D = apparent loss in weight of water
of relative density (R.D) of a substance.
The relative density of a substance was if the weight of equal volume of water
expressed as:
equals the upthrust, then R.D can be
density of a substance written as:
R.D =
density of water
R.D = weight of substance in air
In this chapter, the concept of relative upthrust
density will be discussed using Archimedes’ We know that,
principle. According to Archimedes’
principle, the upthrust acting on the body Upthrust = apparent loss in weight of a
immersed in water is equal to the weight substance,
of water displaced. It is important to note Therefore, R.D can be express as
that, at any location on the Earth’s surface,
the mass of a substance is proportional to weight of substance in air
its weight. Therefore, it is convenient to R.D = apparent loss in weight of water
express the relative density of a substance
in terms of its weight. Thus, the relative density of substances
(both solids and liquids) can also be
m
Since, ρ = , determined by applying Archimedes’
V principle.

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Physics Form 1 Final.indd 103 16/10/2024 20:56