Chapter-Measurement of Length and Motion Science Curiosity class 6 in english Medium CBSE Notes

Chapter 5. Measurement of Length and Motion

Measurement helps us find the exact length, height, or distance of an object. It also helps us understand the movement of objects around us. Standard units and proper measuring methods make our observations accurate and reliable.

Detailed Notes

Measurement

Measurement: Measurement is the process of finding the length, height, width, or distance of an object using a standard unit.

Importance of Measurement

(i) Helps compare different objects.

(ii) Gives accurate results.

(iii) Used in science and engineering.

(iv) Useful in construction, trade, and sports.

Ancient Methods of Measurement

Ancient Methods of Measurement: In ancient times, people measured length using different parts of their body.

Examples of Ancient Units

(i) Handspan

(ii) Cubit

(iii) Footstep

(iv) Finger Width

(v) Arm Length

Limitations of Ancient Units

(i) Measurements were not accurate.

(ii) Body sizes differ from person to person.

(iii) No common standard was available.

Standard Units of Length

Standard Units: Standard units are fixed units accepted all over the world for accurate measurement.

SI Unit of Length

(i) Metre (m)

Common Units of Length

Unit	Relationship
1 kilometre (km)	1000 metres (m)
1 metre (m)	100 centimetres (cm)
1 centimetre (cm)	10 millimetres (mm)

Measuring Instruments

Measuring Instruments: Different instruments are used to measure different objects.

Instrument	Use
Ruler	Small objects
Metre Scale	Large objects
Measuring Tape	Curved or long objects

Correct Method of Measuring Length

Correct Measurement: A measuring scale should be used properly to get accurate readings.

Steps for Correct Measurement

(i) Place the scale along the object.

(ii) Keep the zero mark at one end.

(iii) Read the other end carefully.

(iv) Keep your eye vertically above the scale.

(v) Avoid parallax error.

Using a Damaged Scale

Damaged Scale: A ruler with a broken zero mark can still be used correctly.

Steps to Measure with a Damaged Scale

(i) Start from another clear marking.

(ii) Note the initial reading.

(iii) Note the final reading.

(iv) Subtract the initial reading from the final reading.

Key Points

(i) Measurement gives accurate and reliable results.

(ii) Ancient units were not uniform.

(iii) The SI unit of length is the metre.

(iv) Different instruments are used for different measurements.

(v) Correct reading helps avoid measurement errors.

Measuring Curved Objects

Measuring Curved Objects: Curved objects are measured using a thread or a measuring tape.

Steps to Measure a Curved Object

(i) Place the thread along the curved edge.

(ii) Mark both ends of the thread.

(iii) Straighten the thread.

(iv) Measure it with a ruler.

Reference Point

Reference Point: A fixed object used to describe the position of another object is called a reference point.

Examples of Reference Point

(i) A bus moves with respect to the road.

(ii) A passenger is at rest with respect to the bus.

(iii) The same passenger is in motion with respect to the road.

Importance of a Reference Point

(i) Helps describe position.

(ii) Helps identify rest and motion.

(iii) Makes observations accurate.

Rest

Rest: An object is said to be at rest if its position does not change with time with respect to a reference point.

Examples of Rest

(i) A book kept on a table.

(ii) A parked bicycle.

(iii) A tree standing in a field.

Motion

Motion: An object is said to be in motion if its position changes with time with respect to a reference point.

Examples of Motion

(i) A moving car.

(ii) A flying bird.

(iii) A running child.

Difference Between Rest and Motion

Rest	Motion
Position does not change.	Position changes with time.
Depends on a reference point.	Also depends on a reference point.
Example: Book on a table.	Example: Moving bicycle.

Types of Motion

Types of Motion: Objects move in different ways depending on their path.

Main Types of Motion

(i) Linear Motion

(ii) Circular Motion

(iii) Oscillatory Motion

(iv) Periodic Motion

Linear Motion

Linear Motion: Motion along a straight line is called linear motion.

Examples of Linear Motion

(i) A train moving on a straight track.

(ii) A person walking on a straight road.

(iii) A falling stone.

Circular Motion

Circular Motion: Motion along a circular path around a fixed point is called circular motion.

Examples of Circular Motion

(i) Blades of a ceiling fan.

(ii) Hands of a clock.

(iii) A merry-go-round.

Key Points

(i) A thread is used to measure curved objects.

(ii) Rest and motion depend on the reference point.

(iii) Linear motion follows a straight path.

(iv) Circular motion follows a circular path.

(v) The same object can be at rest or in motion depending on the reference point.

Oscillatory Motion

Oscillatory Motion: The repeated to-and-fro motion of an object about its mean position is called oscillatory motion.

Examples of Oscillatory Motion

(i) A simple pendulum.

(ii) A swing.

(iii) A vibrating guitar string.

Characteristics of Oscillatory Motion

(i) Moves to and fro.

(ii) Repeats its motion.

(iii) Has a mean position.

Periodic Motion

Periodic Motion: Motion that repeats itself after equal intervals of time is called periodic motion.

Examples of Periodic Motion

(i) Oscillation of a pendulum.

(ii) Rotation of the Earth.

(iii) Revolution of the Earth around the Sun.

(iv) Hands of a clock.

Characteristics of Periodic Motion

(i) Repeats after equal time intervals.

(ii) Follows a regular pattern.

(iii) May be linear, circular, or oscillatory.

Applications of Measurement

Applications of Measurement: Measurement is used in many fields to ensure accuracy and precision.

Uses of Measurement

(i) Construction of buildings and bridges.

(ii) Manufacturing industries.

(iii) Medical science.

(iv) Scientific research.

(v) Sports competitions.

(vi) Navigation and transportation.

(vii) Tailoring and garment making.

Ancient Indian Measurement System

Ancient Indian Measurement System: Ancient India used several traditional units to measure length and distance.

Examples of Ancient Indian Units

(i) Angula

(ii) Dhanusa

(iii) Yojana

Importance of Ancient Indian Units

(i) Used before modern SI units.

(ii) Show the knowledge of ancient India.

(iii) Help us understand the history of measurement.

Quick Revision

(i) Measurement helps us find the exact length or distance of an object.

(ii) The SI unit of length is the metre (m).

(iii) A ruler, metre scale, and measuring tape are common measuring instruments.

(iv) A thread is used to measure curved objects.

(v) Rest and motion depend on the reference point.

(vi) Linear motion takes place in a straight line.

(vii) Circular motion takes place along a circular path.

(viii) Oscillatory motion is a to-and-fro motion.

(ix) Periodic motion repeats after equal intervals of time.

(x) Measurement is important in science and everyday life.

(xi) Ancient India used units such as Angula, Dhanusa, and Yojana.

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