Measurement

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Measurement comprises of length, area, volume, mass, density and time.

Universal System of Units is called system international d’ unites (International System of Units) – SI Units.
Below are the major SI Units

Basic Quantity	SI Unit	Symbol
Length	Metre	m
Mass	Kilogram	kg
Time	Second	s
Electric Current	Ampere	A
Thermodynamic	Kelvin	K
Luminous Intensity	Candela	Cd
Amount of Substance	Mole	mol

LENGTH

– The distance between two fixed points.
– The S.I Unit is Metre (M)
Derived units are shown below

Unit	Symbol	Equivalence in Metres
Kilometre	Km	1000
Hectometre	Hm	100
Decametre	Dm	10
Decimetre	dm	0.1
Centimetre	Cm	0.01
Millimetre	mm	0.001
Micrometre	µm	0.000001

Estimating the length of a tree

AREA

– Measures the surface area covered by a body
– Its unit is m².

Can you convert 15.5M² to cm²?

Solution
1m = 100 cm
1m² = 100 cm x 100 cm = 10000 cm²
15.5 m² = 15.5 x 10000 cm²
= 1550000 cm²

Area of a Regular Body

Regular Body	Formulae
Square	L x L
Rectangle	L x W
Circle	πr²
Triangle	½bh
Cylinder	2πDh
Trapezium	½(a+b)h

Remember that π = 22/7 or 3.1429

Area of an Irregular Body

The squares must be 1cm² each.

Area
Full Squares = …. cm²
½ x Incomplete squares = …. cm²
Area = Full Squares + (½ x Incomplete squares)

VOLUME

– Measures the amount of space occupied by a body
– Its unit is m³.

Can you convert 4.5m³ to cm³ ?

Remember: 1m³ = 100cm x 100cm x 100cm = 1000000 cm³

Volume of a Regular Body

NB: Liquids can be measured by putting them into containers with sizes of graduated objects such as Graduate Cylinder, Syringe, Buret and others

Volume of an Irregular Body

It can be done using a Measuring Cylinder or a Eureka Can.

1. Measuring Cylinder

Volume = Q (V1) – P (V2)

2. Eureka Can

Volume will be read on the measuring cylinder.

MASS

– Quantity of matter in a body. SI units is Kilogrammes (Kg)
Mass can be measured using:-

Top Pan Balance
Beam Balance
Lever Balance

DENSITY

– Mass per unit volume. Its symbol is rho (ρ). Its SI Unit is Kilogramme per Cubic Metre (Kg/m³)

A block of stone has a mass of 140g and is 10cm long, 5 cm wide and 4 cm high. Calculate the density of the stone

Solution

Density Using a Density Bottle

The mass of a density bottle is 20g when empty and 45g when filled with water. When filled with liquid x, its mass is 400g. Calculate the density of liquid x. (density of water 1.0 g/cm³)

Solution

Relative Density

Relative density (RD) is the ratio of the density of a substance to the density of water. It is also known as specific gravity (SG).
– If the value is less than 1, it is less dense than water and would float
– If the value is equals to 1, it has the same density as water
– If the value is greater than 1 it is more dense than water and would sink.

Measurement I Quiz 1

Question Instruction:
Answer the question below.

The mass of a 35cm3 of a rare metal was found to be 0.086 kg. Calculate the density of the rare metal in SI Units.

Regular Body	Formulae
Cube	V = S³
Rectangular Prism	V = l x w x hV = Bh
Sphere	V = 4/3πr³
Right Circular Cylinder	V = πr²h
Right Circular Cone	V = 1/3πr²h
Right Square Pyramid	V = 1/3S²h

Darasa Huru

Measurement

LENGTH