Class 6 Science Chapter 5 Measurement of Length and Motion Notes | NCERT Curiosity 2026-27

CLASS 6 SCIENCE NCERT CURiosity | 2026–27

CHAPTER 5

Measurement of Length and Motion

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Clean, student-friendly notes based on the new NCERT Curiosity textbook.

CHAPTER IDEA We use measurement to describe length and distance. We use reference points to describe whether an object is at rest or in motion.

1. How Do We Measure?

Measurement means comparing an unknown quantity with a known unit. A measurement is written using a number and a unit.

NUMBER + UNIT Example: 13 handspans → 13 is the number and handspan is the unit.

In earlier times, people used body-based units such as handspan, foot, finger width, arm length and stride. These were not uniform because body sizes differ.

WHY STANDARD UNITS? A standard unit gives the same measure of the same length to different people. This makes measurements consistent and easy to compare.

2. A Glimpse of Indian Measurement

DID YOU KNOW? Ancient Indian literature mentions units such as angula (finger width), dhanusa and yojana. The angula is still used by some traditional craftspeople such as carpenters and tailors.

3. Standard Units of Length

The internationally accepted system is the International System of Units (SI). The SI unit of length is the metre (m).

Unit	Symbol	Common use
Kilometre	km	Very long distances
Metre	m	Everyday lengths
Centimetre	cm	Small lengths
Millimetre	mm	Very small lengths

KEY CONVERSIONS 1 km = 1000 m   |   1 m = 100 cm   |   1 cm = 10 mm   |   1 mm = 0.1 cm

4. Choose the Right Unit

EASY RULE Large distance → km     |     Room/table → m     |     Pencil/book → cm     |     Tiny thickness → mm

5. Measure Correctly

Good measurement needs correct alignment, careful scale reading and the correct unit.

6. Reading a Scale

·        Keep the scale along the length of the object.

·        Use the zero mark when it is clear.

·        If the zero is damaged, subtract the first reading from the final reading.

·        Keep your eye directly above the mark to avoid parallax error.

7. Measuring a Curved Line

REMEMBER A straight ruler does not follow a curve. A thread can follow the curve, then be straightened and measured.

8. Position and Reference Point

To describe the position of an object, we compare it with a chosen reference point.

CORE IDEA Rest and motion are relative to the chosen reference point. The same object can be at rest with respect to one reference point and in motion with respect to another.

9. Motion

MOTION An object is in motion when its position changes with time relative to a reference point.

REST An object is at rest when its position does not change with time relative to a reference point.

10. Types of Motion

LINEAR / RECTILINEAR MOTION Motion along a straight path. Example: a vehicle moving on a straight road.

CIRCULAR MOTION Motion along a circular path. Example: a merry-go-round or a point on a rotating wheel.

OSCILLATORY MOTION Repeated to-and-fro motion about a position. Example: a swing or pendulum.

PERIODIC MOTION Motion that repeats after equal intervals of time. Circular and oscillatory motions can be periodic.

11. Chapter at a Glance

Concept	Remember
Measurement	Number + unit
SI unit of length	metre (m)
1 km	1000 m
1 m	100 cm
1 cm	10 mm
Reference point	Used to describe position
Motion	Position changes with time
Rest	Position does not change with time
Straight path	Linear / rectilinear motion
Circular path	Circular motion
To-and-fro motion	Oscillatory motion
Repeats after equal intervals	Periodic motion

STUDENT TIP Do not memorise long paragraphs. Understand the idea, look at the diagram, and connect it with something you see in daily life.

Source Note

Prepared from the new NCERT Class 6 Science – Curiosity, Chapter 5, Measurement of Length and Motion (Reprint 2026–27).