Page 112 - Physics

Physics for Secondary Schools

(i) Weight of the stone in air, ( w ). ____N
1
(ii) Weight of the stone in water, ( w ). ____N
2
(iii) Weight of the stone in water + cork in air, ( w ). ____N
3
(iv) Combined weight of the stone + cork (both immersed), ( w ). ____N
4
(v) Weight of the cork in air is obtained by (w – w ). ____N
3 2
(vi) Apparent weight loss of the cork. ____N

(c) Calculate the relative density of the cork using the above information.

A sinker is a solid substance that sinks in water. In this case, it is used to sink with a
body that fl oats on water. In Activity 5.5, the sinker is the stone and the cork is used
as a fl oating body. Then, the relative density of the solid that fl oats can be calculated
as follows,

weight of acork inairair
weight of a cork in
Relative density of a cork (R.D)==
apparent loss in weight of a cork in water
apparent lossinweight acork inwater
w
- w
= w 3 3 - w 2 4

Task 5.5
2. Weigh the stone when it is fully
Repeat Activity 5.5 using kerosene immersed in water inside a beaker
instead of water. How does the and record its weight as w .
2
result compare to the one obtained 3. Remove the stone from the water and
in Activity 5.5? Give reasons for the dry it. Weigh the stone when fully
observation.
immersed in kerosene and record its
weight as w .
Acti vity 5.6 3
Aim: To determine the relative
density of kerosene, using Questions
Archimedes’ principle. (a) Calculate the upthrust in kerosene.
Materials: Stone, beaker, water and (b) Calculate the upthrust in water.
kerosene
Procedure (c) Calculate the relative density of the
1. Using a spring balance, weigh the kerosene.
stone in the air. Record its weight (d) Compare the density of water and
in air as w . kerosene.
1

106
Student’s Book Form One

Physics Form 1 Final.indd 106 16/10/2024 20:56