Chapter 5. Measurement of Length and Motion Science Curiosity class 6 in English Medium ncert book solutions Chapter Review

Chapter 5. Measurement of Length and Motion

The chapter Measurement of Length and Motion introduces students to the importance of measuring length accurately and understanding different types of motion. In everyday life, we measure the length of clothes, roads, furniture, playgrounds, and many other objects. Ancient people often used body parts such as handspan, footstep, arm length, and finger width for measurement. Since these units were different for every person, measurements were not accurate. Therefore, standard units of measurement were developed.

Chapter Review

Introduction to Measurement

Measurement is an important part of our daily life. We measure the length, height, width, and distance of different objects for various purposes. Accurate measurement helps in construction, transportation, education, sports, trade, and scientific experiments. To ensure uniformity and accuracy, standard units of measurement are used all over the world.

Need for Standard Units

In ancient times, people measured length using body parts such as handspan, cubit, footstep, and finger width. Since the size of body parts varies from person to person, these measurements were not reliable. To overcome this problem, scientists introduced standard units that remain the same everywhere.

• Body-part measurements are not uniform.
• Different people obtain different measurements.
• Standard units provide accurate and consistent measurements.
• The International System of Units (SI) is accepted worldwide.

Standard Units of Length

The SI unit of length is the metre (m). Smaller lengths are measured in centimetres (cm) and millimetres (mm), while longer distances are measured in kilometres (km).

Measuring Instruments

Different measuring instruments are used depending on the size and shape of the object.

• Ruler – Small objects such as pencils and notebooks.
• Metre Scale – Tables, doors, and furniture.
• Measuring Tape – Curved objects and body measurements.

Correct Method of Measurement

Accurate measurement requires proper use of measuring instruments.

• Place the scale exactly along the object.
• Keep the zero mark aligned with one end.
• Read the scale with the eye vertically above the marking.
• Avoid parallax error.
• If the zero mark is damaged, begin from another mark and subtract the initial reading from the final reading.

Measuring Curved Length

Curved objects cannot be measured directly with a ruler. A thread or flexible measuring tape is placed along the curved path. The thread is then straightened and measured using a ruler to obtain the correct length.

Reference Point

The position of an object is always described with respect to another object or place called the reference point. Without a reference point, it is impossible to describe the exact position of an object.

Rest and Motion

An object is said to be at rest if its position does not change with time with respect to a reference point. If its position changes with time, the object is said to be in motion.

Whether an object is at rest or in motion depends upon the chosen reference point.

Types of Motion

Linear Motion

When an object moves along a straight path, it is said to have linear motion.

Examples

• A moving train on a straight track.
• A person walking on a straight road.
• A falling stone.

Circular Motion

When an object moves along a circular path around a fixed point, it is said to have circular motion.

Examples

• Hands of a clock.
• Merry-go-round.
• Stone tied to a string.

Oscillatory Motion

When an object moves to and fro about its mean position repeatedly, it is called oscillatory motion.

Examples

• A swing.
• A simple pendulum.
• A vibrating guitar string.

Periodic Motion

A motion that repeats itself after equal intervals of time is called periodic motion. Oscillatory motion and circular motion are common examples of periodic motion.

Ancient Indian System of Measurement

India has a rich history of measurement. Ancient systems used units such as Angula, Dhanusa, and Yojana. Although these units are no longer used for scientific purposes, they show that measurement has been important since ancient times.

Applications of Measurement

• Construction of buildings.
• Road and bridge construction.
• Sports competitions.
• Tailoring and garment making.
• Scientific experiments.
• Engineering and manufacturing.
• Transportation and navigation.

Important Terms

• Measurement
• Length
• SI Unit
• Metre
• Centimetre
• Millimetre
• Kilometre
• Reference Point
• Rest
• Motion
• Linear Motion
• Circular Motion
• Oscillatory Motion
• Periodic Motion
• Parallax Error

Quick Revision

• Measurement helps compare the sizes and distances of objects accurately.
• The SI unit of length is metre (m).
• 1 km = 1000 m.
• 1 m = 100 cm.
• 1 cm = 10 mm.
• Body-part measurements are not standard.
• Use the appropriate measuring instrument for accurate measurement.
• Always read the scale vertically to avoid parallax error.
• Reference points help describe the position of objects.
• An object is in motion if its position changes with time.
• Linear motion occurs in a straight line.
• Circular motion occurs along a circular path.
• Oscillatory motion is a to-and-fro motion.
• Periodic motion repeats after equal intervals of time.
• Standard units ensure uniform measurements throughout the world.

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