MEASUREMENT
❑Measurement refers to the process of finding the size
of a quantity.
❑A quantity is something that can be measured, for
example, distance.
❑Scientists all over the world have one international
system of units i.e. systeme internationale de unites
(SI units) for physical quantities.
Types of Physical Quantities
- There are two types of physical quantities, namely:
a) Basic Physical Quantities (Fundamental Physical Quantities)
b) Derived physical quantities
Basic Physical Quantities
- These are quantities that cannot be obtained from other physical
quantities.
- They are as shown in the table below:
Basic physical quantity SI unit Symbol of the
SI unit
Length Meter m
Mass Kilogram kg
Time Second s
Electric current Ampere A
Temperature Kelvin K
Luminous intensity Candela Cd
Amount of substance mole mol
Derived Physical Quantities
- These are quantities obtained by multiplication or division of
other physical quantities e.g. area, volume, work, density,
momentum etc.
LENGTH
It is the measurement of distance between two points. Examples of
length are:
•breadth
•diameter
•height
•depth etc.
SI unit of length is meters(m).
Other multiple units are centimeter(cm), millimeter(mm) and
kilometer (km).
1 km = 1 000 m
1 m = 100 cm
1 cm = 10 mm
Assignment
Convert the following metric units
a) 500 cm = _______________ m
b) 45 m = _________________cm
c) 350 000 cm = ___________ km
d) 750 mm = ______________ m
e) 7 km = _________________ mm
f) 120 mm = ______________ cm
g) 23 000 m = _____________ km
MEASUREMENT OF LENGTH
The common instruments used for measuring length are:
1. Meter rule
2. Tape measure
HOW TO READ THE METER RULE
• Meter rule is graduated in cm and mm.
• Its accuracy level is a 0.1 cm.
• The accuracy of measuring instrument is the smallest unit an instrument
can measure.
Procedure for using a meter rule:
a)Place the meter rule in contact with the object.
b)Place the end of the object against zero mark on the scale.
c)Position your eye perpendicularly above the scale to avoid error of
parallax.
Task
What are the readings indicated by arrows P, P1, P2, and P3 below.
Experiment 2.1
Aim/ Objective
•To measure the circumference of a measuring cylinder using a
thread
Apparatus
•10 ml measuring cylinder/ glass
•Thread
•Meter rule
Procedure
•Closely wrap a thin thread ten times around the cylinder as shown
below.
Homework
1. The diagram shows an enlarged drawing of the end of a metre
rule. It is being used to measure the length of a small feather.
What is the length of the feather?
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Example
Estimate the area of the irregular surface shown in the figure below by
counting the small squares. The area of one complete square is 1cm2.
Task
Estimate the area of the irregular surface shown in the figure
below by counting the small squares. The area of one complete
square is 1cm2.
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Volume of regular shapes
Measuring Volume of Irregular - Shaped Solids
Experiment
Aim: To measure volume of irregularly – shaped solid
Requirements: stone, thread, measuring cylinder and water
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Task
A measuring cylinder contains some water. When a
stone is put in the water, the level rises. What is the
volume of the stone?
MASS
•Mass is a quantity of matter in a body.
•Its S.I unit is kilograms (Kg)
The multiples and submultiples include;
1 kg = 1000 g (gram)
1 000 kg = 1 tonne
1 g = 1 000 g
Mass is measured using:
(i) Beam balance or
(ii) Electronic balance (top pan balance).
Task
The following is an instrument that is used for measurement in the
laboratory.
What is the name of the instrument?
Which basic physical quantity does the instrument measure?
What is the reading of the instrument?
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2. All the sides of a plastic cube are 8.0 cm long. Figure below shows the
cube
The mass of the cube is 1536 g.
(a) Explain what is meant by mass.
................................................................................................................................... [1]
(b) Calculate the density of the plastic from which the cube is made.
density = ...........................................................[2]
Time
- Time is the duration of an activity.
- Time is measured using a stopwatch.
- Time is measured in seconds.
Example
The diagram shows a stopwatch.
What is the reading on the stopwatch?
