- This lesson will help you to:—
- understand non-uniform units.
- revise standard units of length like millimeter,
- centimeter and meter.
- choose appropriate standard unit of length.
- measure objects using standard unit of length.
- estimate length of a given object in standard units.
- verify length of a given object by measuring.
- use a ruler for measuring length.
- relate centimeter and meter.
Real life examples
- All clothes are stitched by taking body measurements using measuring tapes.
- Measurement of length helps in knowing the distance between two places.
- Carpenters use measuring tapes to measure length of wooden furniture in order to construct them.
- All students in your class are of different heights.
- The size of your shoe is based on the length of your feet.
Meters (m) is the unit which is widely used in various races like car race, bicycle race.
- Fathom: “The length of the outstretched arm”, about six feet. Water depth is measured in fathoms.
- Span: “The distance between the thumb and little finger of an extended hand” roughly nine inches.
QUICK CONCEPT REVIEW
Rulers are used to measure small objects.
You can measure the length of the pencil using a ruler.
This pencil is 5 cm long. Try measuring your pencil.
Measuring tapes are used to measure large objects.
Measuring tape is also used to measure body parts.
- Have you ever measured your fingers? The middle finger is 4.5 cm long. Try measuring your fingers!
- Have you ever measured your waist? Oops!! Looks like Hippopotamus is having short of measuring tape. Try measuring your waist and see whether you face the same problem.
MEASUREMENT USING RULER OR MEASURING TAPES
Place one end of the object with ‘0’ in the ruler/measuring tapes.
The object and the ruler/measuring tapes should be straight.
Start reading the scale on ruler/measuring tapes.
Stop reading the scale where the object ends.
Hold the last end of the object and read the scale.
SHORTCUT TO PROBLEM SOLVING
- Always start from '0' while using measuring instruments.
- Millimeter (mm) and centimeter (cm) are used to measure very small distance.
- Meter (m) and kilometer' (km) are used to measure large distances.
LET’S UNDERSTAND SOME CONVERSIONS
- 100 Centimeters = 1 Meter
100 cm =1 m
- 10 Centimeters = 1 decimeter
- 10 decimeters = 1 meter
- In ancient times, various body parts were used to measure objects.
- It was the Greeks who developed the “foot” as their fundamental unit of length. It was based on an actual measurement of Hercules’ foot.
- Qutub Minar is the tallest minaret in India. It is 72.5 Meters high
Misconcept: All the units of measuring the volume are equal.
Concept: Different units of measuring volume vary in their capacity. The volume must not be interchanged.
Misconcept: Some large rulers can measure long distances.
Concept: Rulers cannot be used to measure long distances, irrespective of how big the ruler be. A ruler cannot be used to measure units such as kilometers.