1.6 Discussion Activity

Physical quantity

SI Unit Symbol

Length metre m

Mass Kilogram Kg

Temperature Kelvin K

Electrical current

Ampere A

Time second s

MASS

• The mass of an object is the quantity of matter contained in the object.

• The SI unit for mass is kilogram (kg).

WEIGHT

• The earth pulls objects to its centre.

This pull is called the force of gravity or gravitational force.

• The weight of an object is the pull of the Earth on the object

• The SI unit for weight is Newton (N).

Which one is heavier?

WEIGHT AND MASS

Quantity of matter contained in an object.

The pull of the Earth’s gravity on that object.

Kilogram (kg) Newton (N)

Lever balanceTriple beam balance

Newton spring balanceCompression balance

Mass of an object does not change

Weight of an object changes from place to

place

Not effect by gravity Effect by gravity

MASS WEIGHTDIFFERENCES

DEFINITION

SI UNIT

MEASURINGTOOLS

CHARACTERISTICPROPERTY

Also measured in grams(g) and miligrams(mg) 1 kg=1 000 g 1 g=1 000 mg

Relationship between weight and mass:

1 N = 100 g10 N = 1 000 g = 1 kg

Why weight of an object changes from place to place?The Earth’s gravitational pulls different in different places.- Weight of an object is heavier at the North Pole and South

Pole than at the equator.The moon gravitational pull is only 1/6 of the Earth’s.- Example:

An astronaut weighing 600 N on the Earth will weigh only 100 N on the moon.

WEIGHT AND MASS

MEASURING TOOLS

1) Measurement of length2) Measurement of the diameter of an

object3) Measurement of area4) Measurement of volume of liquid5) Measurement of volume of solids

Measurement of lengthWhat is length?

Length is the distance between two points.The SI unit for length is metre(m),but the units kilometre(km), centimetre(cm) and milimetre(mm) are also used.

How length can be measured?

Topic :

1 cm = 10mm1 m = 100 cm

1 km = 1000 m

Length Measuring tools

1) Straight line Metre rulerMeasuring tape

2) Curved line Thread and rulerOpisometer

NOTE: To get accurate or precise reading, three(3) measurements are usually taken

What is diameter?• A straight line drawn from side to side through

the centre of circle.

How diameter can be measured?

Measurement of diameterTopic :

diameter

2 types

Internal diameter External diameter

Diameter Measuring tools1)Internal diameter Internal calipers and ruler2)External diameter External calipers and ruler

What is area?Area is the total surface or space occupied by an objectThe units for area are square metres (m²)

square centimetres (cm²)square milimetres (mm²)

Area of How to calculate

1)Square/

rectangle

Area = length x width

2) Triagle

Area =(½ )x base x height

Measurement of AreaTopic :

Types of areaArea of regular shapes Area of irregular shapes

Estimated by using graph paperExamples: leaves & petals

√ √ √ √

X X X √

√ √

What is area?Area is the total surface or space occupied by an objectThe units for area are square metres (m²)

square centimetres (cm²)square milimetres (mm²)

Area of How to calculate

1)Square/

rectangle

Area = length x width

2) Triangle

Area =(½ )x base x height

Measurement of AreaTopic :

Types of areaArea of regular shapes Area of irregular shapes

Estimated by using graph paperExamples: leaves & petals

√ √ √ √

X X X √

√ √

What is volume?Volume is the total space occupied by an objectThe units for volume are cubic metres (m³)

cubic centimetres (cm³)cubic milimetres (mm³)liters (∫) and

mililitres(m∫)

Measurement of VolumeTopic :

Types of volume

Volume of liquids Volume of solids

1 m∫ = 1 cm³ 1 ∫ = 1 000 m∫ = 1 000 cm³

Measured by:Measuring cylinderPipetteBurette

Determined by using water displacement method

Regular-shaped Irregular-shaped

2 types of solids

What is volume?Volume is the total space occupied by an objectThe units for volume are cubic metres (m³)

cubic centimetres (cm³)cubic milimetres (mm³)liters (∫) and

mililitres(m∫)

Measurement of VolumeTopic :

Types of volume

Volume of liquids Volume of solids

1 m∫ = 1 cm³ 1 ∫ = 1 000 m∫ = 1 000 cm³

Measured by:Measuring cylinderPipetteBurette

Determined by using water displacement method

Regular-shaped Irregular-shaped

2 types of solids

End of chapter 1