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CBSE Class 6 · Science

Measurement of Length and Motion

Official NCERT chapter from Curiosity (book code fecu1). ExamMaster notes are original teaching at CBSE Class 6 depth.

This lesson follows the official chapter “Measurement of Length and Motion” in Curiosity. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.

  • CBSE Class 6
  • Easy level
  • 8 concepts

1How do we Measure?

Measure means compare a length to a unit you can say: this table is 4 hand-spans, or 120 centimetres. A “long” with no unit is a feeling.

A body-part unit changes with the person. That is why a later idea will demand a standard.

Figure. A hand-span changes with the hand. Two people can count 4 and 5 spans on the same desk. A marked scale gives one length, here 80 cm.

How it works

  1. Choose a unitHand-span, or a marked scale.
  2. Lay it without gaps or overlapsA count.
  3. Write number and unit together4 spans, not “4”.

2Standard Units

A standard unit is a unit everyone in the class can share: metre, centimetre, millimetre. Your hand-span is useful at home; it is not the class standard.

Mixing metres and centimetres without converting is two languages at once.

Figure. Length needs a shared unit. The SI unit is the metre. 10 mm make 1 cm; 100 cm make 1 m; 1000 m make 1 km.

How it works

  1. Pick the standard that fits the sizemm for a pencil-width; m for a room.
  2. Keep one unit in one sentence when you canOr convert.
  3. Refuse “about this much” as the only recordA number plus a unit.

3Correct Way of Measuring Length

A scale starts at the zero mark, sits along the length, and is read at the other end. Starting at 1 and forgetting to subtract is a miss.

A scale held at an angle shortens the reading.

Figure. Seat the zero mark at the object’s end, and read the other end. Starting at 1 cm and reading 9 cm names 8 cm wrongly as 9.

How it works

  1. Place the zero on one endOr note the start-mark and subtract.
  2. Keep the scale along the objectNo tilt.
  3. Read the other endNumber plus unit.

Zero on the end

A pencil’s tip sits on the 0 cm mark. The other tip is at 14 cm. How long is the pencil?

  • Start0 cm
  • End14 cm
  • Length14 cm

Pro tip. If the start had been 1 cm, length would be end minus start.

4Measuring the length of a curved line

A curved path is not a straight scale. Lay a thread along the curve, mark the ends, then straighten the thread on a scale.

A straight scale laid as a chord under-reads the curve.

Figure. A curve is measured by laying a thread along it, then stretching that thread on a scale. The path is short segments because this drawing has no arc.

How it works

  1. Follow the curve with threadNo slack if you can help it.
  2. Mark the two ends on the threadA segment.
  3. Straighten and read on a scaleThe curve’s length.

5Describing Position

Position needs a reference: 3 m from the door, toward the window. “Here” without a reference is a finger, not a record.

Two people can say “near the tree” and mean different spots.

Figure. A position is a distance from a named landmark. “5 m from the tree” names the tree first. A lone “5 m” has no place.

How it works

  1. Name a referenceDoor, tree, origin on a line.
  2. Give a distance and a direction if you can3 m toward the gate.
  3. Write bothPosition is a pair.

6Moving Things

Motion is a change of position with time. A book that stays 2 m from the door is at rest relative to the door. The same book on a moving bus is moving relative to the road.

Rest and motion need the reference you named.

Figure. A thing is moving when its place relative to a landmark changes. The left box stays at A. The right pair shows the same thing after the place changed.

How it works

  1. Name the objectThis book.
  2. Name the referenceDoor, or road.
  3. Ask whether position vs that reference changedMove, or rest.

7Types of Motion

Name the path if you can: along a straight line, to and fro (oscillation), around a point (circular), or a mix. The type is the path-test, not the object’s name.

A car can do more than one type on different stretches.

Figure. Straight is one direction. To-and-fro repeats the same line. Around returns to the start. A circle would need an arc, so around is a closed rectangle here.

How it works

  1. Watch the pathStraight, swing, circle, mix.
  2. Name that type for this stretchOne case.
  3. Do not freeze the object as “always circular”The path can change.

8Start a scale at zero; a number without a unit is mute

Zero-at-the-end is the clean start. A reading “12” could be 12 cm or 12 m — mute until the unit sits next to it.

Starting at 1 and calling the end-mark the length is a miss unless you subtract.

Figure. Start the scale at its zero mark. Write the unit with the number. Bare 8 is mute; 8 cm is a length.

How it works

  1. Park zero on one endOr subtract start from end.
  2. Write the unitcm, m, mm.
  3. If the unit is missing, refuse the number as a lengthMute.
A curved line is measured by
  1. Thread along the curve, then a scale on the thread
  2. A straight scale as a chord only
  3. Guessing spans

Straighten the thread.

Notes

  • Mapped to the official NCERT chapter “Measurement of Length and Motion”. Original teaching only — no textbook sentences.
  • Science here is Physics, Chemistry and Biology ideas at this class, never a language or social-science chapter.

Formulas

  • Length = end-mark − start-mark (same unit)
  • 1 m = 100 cm = 1000 mm

Recap

Hold these pegs from the official chapter “Measurement of Length and Motion”. The wording is ExamMaster’s teaching, not a textbook recap.

How do we Measure?
Measure means compare a length to a unit you can say: this table is 4 hand-spans, or 120 centimetres.
Standard Units
A standard unit is a unit everyone in the class can share: metre, centimetre, millimetre.
Correct Way of Measuring Length
A scale starts at the zero mark, sits along the length, and is read at the other end.
Measuring the length of a curved line
A curved path is not a straight scale. Lay a thread along the curve, mark the ends, then straighten the thread on a scale.
Describing Position
Position needs a reference: 3 m from the door, toward the window.
Moving Things
Motion is a change of position with time. A book that stays 2 m from the door is at rest relative to the door. The same book on a moving bus is moving relative to the road.

Practise Measurement of Length and Motion

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  • A 4-question practice set that ends the chapter
  • 1 quick check with worked explanations
  • Timed mocks scored with the real marking scheme
  • Readiness tracked per topic, kept on your device
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