Page 58 - Physics

Physics for Secondary Schools
water level would be lower than the spout
level. It would also interfere with the
volume to be measured.
The water in the eureka can is displaced
so as to give room for the stone. The stone
occupies a volume which is equal to the
volume of water displaced.
If the solid has an irregular shape such as
a stone, it is submerged in a measuring
cylinder containing water and the volume
of water displaced is taken as the volume
of the solid. Note that, the method of
immersion can also be used to measure
the volume of regular object.
Measurement of volumes of gases
A gas always fi lls any container into which
it is placed. Therefore, the volume of a
gas can be determined by measuring the
volume of the container that hold the
gas. The volume of the container can be
determined from its dimensions or by
fi lling it with water and then pouring the
water into a measuring cylinder.
Exercise 2.4
1. Calculate the volume of a cube of
sides 2 cm.
2. The volume of a brick is given as
60 cm . Given that its length and
3
width are 6 cm and 4 cm respectively,
calculate its height.
3. A cylindrical container has a
diametre of 10 cm and a height of
12 cm. Calculate its volume, given
that π = 3.14.
4. A beaker contains 100 cm of liquid.
3
A 25 cm pipette is used twice to
3
transfer the liquid to another beaker.
What is the volume of the liquid left
in the original beaker?
52
Physics Form 1 Final.indd 52
5. The initial volume in a burette was
read as 80 cm . Suppose X cm 3
3
of the liquid was run out and the
fi nal volume was read as 57 cm .
3
Calculate the value of X.
6. What is the volume of an irregular
3
solid immersed in 50 cm of water
contained in a beaker if it raises the
3
water level to 57 cm .
Sources of errors
While taking any measurement, there
may be some error in the reading. An
error is defi ned as a deviation from the
actual reading. However, there is a more
precise defi nition. An error is a measure of
estimated difference between the measured
value and the actual value of a physical
quantity that is being measured or observed.
Errors usually arise due to several reasons:
1. An instrument fault during manufacture
– If a measuring instrument is not
manufactured as per specifi cation, then
the accuracy is lowered.
2. Damage during use – Bad handling
of instruments can lead to incorrect
results. Each apparatus should be used
properly and for the right purpose.
3. Poor storage – Apparatus should be well
stored away from factors that affect
their accuracy like dust and heat.
4. Human factors – Errors can arise
when an experimenter does not take
readings from an instrument properly.
There are three common errors caused
by improper reading of an instrument
these are:
(i) Parallax error;
(ii) Zero error; and
(iii) Instrumental error
Student’s Book Form One
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