Chapter 1:Measurements
Physical quantities are quantities that can be measured.To describe a physical
quantity, we first define the unit in which the measurement is made.There are
many systems of units but the most common system of units used by scientists is
based on the metric system.
We can represent a physical quantity by the symbol of the quantity, the numerical
value of the magnitude of the quantity and the unit of m of 8 m.
Measurement of the quantity. For example,Figure 1.1 shows a footballer scoring a
goal.The ball was kicked a distance
There are two types of physical quantities,that is,base quantities and derived
quantities.
Base quantities are physical quantities that cannot be defined in terms of other
quantities.Table 11 shows seven base quantities and their respective S.I. units.
Derived quaintities are physical quantities derived from combinations of base
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quantities through multiplication or division or both multiplication and division.
Questions:
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4.
5.
Prefixes:
1. Prefixes are used to simplify the description of physical quantities that are
either very big or very small in S.I.units.
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2. Table 1.3 lists some commonly used SI prefixes and their multiplication factors.
Standard Form
1. The distance of Pluto from the Earth is about 6 000 000 000 000 m and the
radius of a hydrogen atom is about 0.000 000 000 05m.These quantities are either too
large or too small and a simpler way of expressing them is by using standard form of
representation or scientific notation.
2. In a standard form or scientific notation, a numerical magnitude can be
written as:
Hence, the distance of Pluto from the Earth can be written as6x1012m and the radius
of a hydrogen atom as 5x10 -11m.
Questions:
6. For each of the following, express the magnitude using scientific notation.
(a) The length of a virus =0.000 000 08 m
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(b) The mass of a ship =75 000 000 kg
Scalar and Vectors
a scalar is a quantity that only has magnitude (size), while
a vector has both magnitude and direction. Examples of scalar
quantities include pure numbers, mass, speed, temperature, energy,
volume, and time. Examples of vector quantities include velocity,
acceleration, momentum, displacement, and forces, such as weight
and friction.
Question:
7
5
8
6
9.
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Answer:
a) i) Scalar quantities are physical quantities that have magnitude
only.
ii) Vector quantities are physical quantities that have magnitude and
direction.
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B
c)
Choice Reason
The temperature scale should Using a Celsius scale is more
be in degree Celsius. convenient in this research
project
The temperature range should Such a temperature range can
have a minimum value which is accommodate the required
smaller than 10°C and a range of 10°C to 125°C based
maximum value which is bigger on the criteria
than 125°C.
The liquid in the thermometer is Mercury is a good conductor of
mercury. heat and quickly changed when
the environmental temperature
change
The colour of the thermometer This will make it easier for
liquid should be opaque observers to take readings on
the thermometer
Thermometer R is chosen.because Thermometer R has a Celsius
scale, a temperature range of –10°C to 200°C, is filled with
mercury and is opaque.
(d) (i) 2°C dan 85°C (ii) 2°C – 0°C = 2°C
There are impurities in the ice used.
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