CBSE Class 6 Science Revision Notes Chapter 5: Measurement of Length and Motion

Measurement compares an unknown length with a selected unit, while motion describes a change in position with time.

In CBSE Class 6 Science, metre is the SI unit of length and motion is identified using a reference point.

Measurement helps us describe the length, height or distance of an object accurately. Earlier, people used body parts such as handspans, feet and arm lengths, but these produced different answers.

These notes follow the current 2026–27 chapter. Use them to revise standard units, measuring tools, reference points and types of motion.

Key Takeaways

• SI unit: The standard SI unit of length is metre, written as m.
• Unit conversions: 1 km = 1000 m, 1 m = 100 cm and 1 cm = 10 mm.
• Reference point: Motion and rest are decided by comparing an object’s position with a fixed point.
• Three main motions: Linear, circular and oscillatory motions are identified by their paths.

Access Class 6 Science Chapter 5 Measurement of Length and Motion Notes in 30 Minutes

Revise the chapter in three parts:

• First 10 minutes: Traditional measurements, standard units and unit conversions
• Next 10 minutes: Measuring tools, correct scale use and curved-line measurement
• Final 10 minutes: Reference points, motion, rest and types of motion

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Measuring Length in Class 6 Science Chapter 5 Notes

Length tells us how long, tall or wide an object is. It can also describe the distance between two places.

To measure length, we compare it with a chosen unit.

Traditional Ways of Measuring Length

Before standard scales became common, people used parts of the body to measure length.

Common traditional units included:

• Handspan
• Finger width
• Foot length
• Arm length
• Fist
• Stride

A farmer might measure a field by counting strides. A tailor or carpenter might use finger widths or the length of an arm.

Why Are Body-Based Units Unreliable?

The size of a handspan, foot or arm differs from person to person.

Suppose five students measure the same table using their handspans. Their answers may differ because their handspans are not equal.

Therefore, body-based units cannot give the same result for everyone.

Number and Unit in Measurement

Every measurement has two parts:

1. A number
2. A unit

For example, if a table measures 13 handspans:

• 13 is the number.
• Handspan is the unit.

Writing only the number does not give complete information.

Ancient Indian Units of Length

India has a long history of measurement.

Some units mentioned in ancient Indian literature include:

• Angula
• Dhanusa
• Yojana

Angula referred to finger width. Traditional craftspeople such as carpenters and tailors may still use similar measurements.

Ruled objects found at Harappan sites show that people used organised systems of measurement in ancient times.

Standard Units in Class 6 Science Chapter 5 Revision Notes

Measurements must remain the same when different people measure the same object correctly.

Countries therefore adopted a common system called the International System of Units, or SI units.

SI Unit of Length

The SI unit of length is the metre.

Its symbol is:

m

One metre is divided into 100 equal centimetres.

Main Units of Length

Units of Length Conversion

The important conversions are:

1 km = 1000 m

1 m = 100 cm

1 cm = 10 mm

Therefore:

1 m = 1000 mm

Understanding a 15 cm Scale

A common geometry-box scale has markings from 0 cm to 15 cm.

The distance between two consecutive centimetre marks is 1 cm. Each centimetre is divided into 10 smaller parts.

Each small division represents 1 mm.

Therefore, the smallest length measured using this scale is usually 1 mm.

Choosing a Suitable Unit

The unit should match the size of the object or distance.

Using kilometres for an eraser or millimetres for the distance between cities would be inconvenient.

Inch as a Unit

Some scales also contain inch markings.

1 inch = 2.54 cm

Inches and feet were commonly used earlier. Some people still use them, but the chapter mainly follows SI units.

Correct Measurement of Length Notes for Class 6

Accurate measurement requires a suitable tool and the correct method.

A small error in scale placement or eye position can change the result.

Selecting the Right Measuring Tool

Different objects require different tools.

Rigid scales are suitable for straight lengths. Flexible tapes work better around curved surfaces.

Correct Way to Place a Scale

Place the scale:

• In contact with the object
• Along the object’s length
• With one end of the object aligned to a clear scale mark

The scale should not be slanted or placed away from the object.

Correct Eye Position

The eye should remain directly above the point where the reading is taken.

Looking from the left or right can make the scale marking appear different.

A direct eye position gives a more accurate reading.

Measuring with a Broken Scale

A scale can still be used if its zero end is broken.

Start from another clear full mark, such as 1 cm. Note the reading at the other end and subtract the starting reading.

Length = Final reading − Initial reading

Example:

Initial reading = 1.0 cm

Final reading = 10.4 cm

Length = 10.4 cm − 1.0 cm

Length = 9.4 cm

The subtraction step is essential. The final reading alone is not the object’s length.

Scales for Visually Challenged Learners

Visually challenged learners may use scales with raised markings.

These markings can be felt by touch and help them measure lengths.

Rules for Writing Units

Follow these rules when recording measurements:

• Write unit names in lowercase.
• Write symbols such as km, m, cm and mm in lowercase.
• Do not add “s” to a plural symbol.
• Leave a space between the number and symbol.
• Do not add a full stop after the symbol unless it ends a sentence.

Correct examples:

5 cm

12 m

3 km

Incorrect examples:

5cms

12M

3 k.m.

Measuring Curved Lines in Measurement of Length and Motion Notes

A rigid scale cannot follow a curved path accurately.

Curved lengths can be measured using:

• Flexible measuring tape
• Thread

Thread Method for a Curved Line

1. Place a thread carefully along the curved line.
2. Mark the thread at the beginning and end of the curve.
3. Remove the thread.
4. Straighten it without stretching.
5. Measure the marked part using a scale.

This method can measure:

• The boundary of a leaf
• The curved base of a bottle
• Decorative string lights
• The outer boundary of a wheel

The thread should not be stretched because stretching changes its length.

Reference Point in Chapter 5 Science Revision Notes

The location or position of an object must be described in relation to another object or point.

A fixed object or point used for this comparison is called a reference point.

Describing Position

Suppose students describe whether a garden is close to their houses.

Their answers may differ because each house is at a different location. If they all compare the garden with the same bus stand, their descriptions become easier to compare.

The bus stand then acts as the reference point.

Reference Point in a Kabaddi Court

Before drawing a Kabaddi court, students select one fixed point on the ground.

They measure all required distances from this point. This keeps the court lines properly placed.

Kilometre Stones and Position

A kilometre stone reading “Delhi 70 km” means the location is 70 km from Delhi.

When the next stone reads “Delhi 60 km,” the traveller is now 60 km from Delhi.

Delhi is the reference point in both readings.

The changing number shows that the traveller’s position relative to Delhi is changing.

Motion and Rest in Class 6 Science Chapter 5 Notes

Motion and rest cannot be decided without a reference point.

The position of an object must be compared with the same reference point over time.

Motion

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

Examples include:

• A moving bus
• A falling fruit
• A flying bird
• A rolling ball
• A walking person

Rest

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

Examples include:

• A tree beside a road
• A book on a table
• A parked bicycle
• A chair in a classroom

Motion and Rest Comparison

Passengers in a Moving Bus

Passengers sitting inside a moving bus appear at rest relative to the bus.

Their positions on the seats do not change.

However, they are in motion relative to buildings and trees outside. Their position compared with these outside objects keeps changing.

Therefore, the same person may be:

• At rest relative to the bus
• In motion relative to a roadside building

This shows why a reference point is necessary.

Types of Motion in Measurement of Length and Motion Revision Notes

Objects follow different paths while moving.

The chapter introduces linear, circular and oscillatory motion.

Linear Motion

When an object moves along a straight line, it shows linear motion.

Examples include:

• An eraser falling vertically
• A fruit dropping from a tree
• Students marching in a straight line
• A box pushed along a straight path
• A car moving on a straight road

The path may be horizontal, vertical or sloping, but it remains straight.

Circular Motion

When an object moves along a circular path, it shows circular motion.

Examples include:

• A child on a merry-go-round
• An eraser whirled using a thread
• The hands of a clock
• A point on a rotating fan blade
• A stone tied to a string and rotated

The object moves around a fixed central point.

Oscillatory Motion

When an object moves to and fro about a fixed position, it shows oscillatory motion.

Examples include:

• A swing
• A simple pendulum
• A hanging eraser moving to and fro
• A vibrating metal strip
• A child moving back and forth on a swing

The object repeatedly moves on either side of its fixed position.

Linear, Circular and Oscillatory Motion

Periodic Motion in Class 6 Measurement of Length and Motion Notes

Motion that repeats after a fixed interval of time is called periodic motion.

Circular motion may be periodic when the object repeatedly completes the same circular path.

Oscillatory motion is also periodic when the object repeats its to-and-fro movement at regular intervals.

Examples include:

• Hands of a clock
• A regularly moving pendulum
• A rotating fan
• A swing repeating its movement

A motion can therefore be both circular and periodic, or oscillatory and periodic.

Can One Object Show More Than One Type of Motion?

Yes, an object may show different motions at the same time.

For example, a bicycle wheel moves forward with the bicycle while also rotating.

The wheel therefore shows:

• Forward motion with the bicycle
• Circular motion around its axle

A ball on a curved rollercoaster track may show different types of motion on different portions of the track.

The type depends on the path being followed at that moment.

Class 6 Science Chapter 5 Summary Notes

Important Terms from Measurement of Length and Motion

Length: The measure of how long an object or distance is.

Measurement: Comparing an unknown quantity with a selected unit.

Unit: A fixed quantity used for measurement.

SI units: Internationally accepted standard units of measurement.

Metre: The SI unit of length.

Reference point: A fixed point used to describe position or motion.

Distance: The length between two points.

Motion: Change in an object’s position relative to a reference point with time.

Rest: A condition in which position does not change relative to a reference point.

Linear motion: Motion along a straight line.

Circular motion: Motion along a circular path.

Oscillatory motion: Repeated to-and-fro motion around a fixed position.

Periodic motion: Motion that repeats after a fixed interval.

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