Page 51 - Physics

Measurement

Exercise 2.3 Table 2.8: Derived physical quantities and
their SI units
1. Imagine you want to fi nd out how
long a piece of wire is. While doing Physical SI unit Unit
this, you come across two terms: quantity symbol
estimated length and measured Area Square metre m 2
length. How do these terms differ?
2. Why do we need to measure things? Volume Cubic metre m 3
3. Outline fi ve (5) different items found Weight Newton
in your environment that can be N
measured in terms of: Density kilogram per kg/m 3
(a) Length (b) mass cubic metre
4. A Form One student was asked Pressure newton per N/m 2
to measure time for conducting a square metre
science experiment. What items
could the student use to accurately These quantities are calculated using
measure time? certain formulae or they are determined
5. Suppose a teacher asks you to experimentally. For example, Area (A) of a
2
determine the mass of water in a square = length (l) × length (l) = l × l = l .
measuring cylinder. How would you The SI unit of area is the square metre, m .
2
do it using a digital balance? However, areas of other regular shapes are
6. Imagine you are using a digital calculated using their respective formulae
balance to measure the mass of a depending on the shape of the object.
metallic ball. What is the unit of the
reading on the electronic balance? Measurement of volume
Volume is the quantity of space that an
Derived quanti ti es object occupies. The SI unit of volume is
3
Derived quantities are obtained by cubic metre (m ). One cubic metre is the
volume of a cube with sides that are one
combining the fundamental quantities metre long. Other units of volume include:
through the application of basic arithmetic (a) cubic centimetre (cm );
3
operations, namely multiplication and/or
division. Their units are called derived units (b) millilitre (ml); and
and the same method is used in deriving (c) litre (l).
them. Examples of derived quantities
are area, volume, density, velocity and Relative to everyday school laboratory
acceleration. Their respective derived works, a cubic metre is rather a large unit of
2
2
SI units are m ,m ,k /m , m/g 3 s and m/s . volume. Therefore, convenience purposes,
3
Table 2.8 shows some derived quantities volumes are measured using the cubic
3
and their corresponding SI unit. centimetre (cm ). One cubic centimetre is
45

Physics Form 1 Final.indd 45 16/10/2024 20:55