Chapter 9: Motion and Measurement of Distances 📏
A Comprehensive Guide for PSTET Paper-2 (Science)
Chapter Overview
| Section | Topic | PSTET Weightage | Page No. |
|:---:|:---|::---:|:---:|
| 9.1 | Story of Transport | Medium | 2 |
| 9.2 | Measurement: Standard and Non-standard Units | High | 6 |
| 9.3 | Correct Way of Measuring Length | High | 11 |
| 9.4 | Types of Motion (Rectilinear, Circular, Periodic) | High | 15 |
| Practice Zone | MCQs & Pedagogical Questions | - | 20 |
Learning Objectives 🎯
After studying this chapter, you will be able to:
✅ Trace the evolution of transport from ancient times to the modern era
✅ Differentiate between standard and non-standard units of measurement with examples
✅ Explain the correct method for measuring length using a ruler
✅ Identify and classify different types of motion—rectilinear, circular, and periodic
✅ Apply pedagogical strategies to teach motion and measurement concepts effectively to upper primary students
Pedagogical Link 🔗
For Teachers: This chapter directly aligns with:
Class 6 Science NCERT Chapter 10: "Motion and Measurement of Distances"
Teaching Tips:
Take students for a "Measurement Walk" around the school to estimate and measure distances
Use body parts (handspan, cubit, pace) to introduce non-standard units before standard units
Create a "Motion Museum" with examples of different types of motion
Use simple experiments like rolling a ball to demonstrate rectilinear motion
Connect to history and social studies when teaching the story of transport
Section 9.1: Story of Transport 🚗
Introduction
Transport has played a crucial role in the development of human civilization. From walking barefoot to travelling in spaceships, the journey of transport is a fascinating story of human innovation and ingenuity. The need to move people and goods from one place to another has driven countless inventions throughout history .
9.1.1 The Evolution of Transport Through Ages
Table 9.1: Timeline of Transport Development
9.1.2 Detailed Journey Through Transport History
A. Early Beginnings: Walking and Animal Transport 🚶
In ancient times, people travelled on foot and carried goods themselves. The first earth tracks were created by humans carrying goods, and these tracks often followed animal trails. As animals were domesticated—horses, oxen, and donkeys—they became an important element in track-creation and transport .
Key Facts:
A horse can carry about 125 kg of load
The average overland speed by horse was around 8 kilometers per hour
B. The Revolutionary Invention: The Wheel 🎡
The invention of the wheel around 3500 BC in the ancient Near East was a turning point in human history. Animal-drawn wheeled vehicles spread to Europe and India in the 4th millennium BC and to China around 1200 BC .
Before the Wheel: The number of things people could transport over long distances was limited
After the Wheel: Heavier loads could be moved; trade expanded significantly
C. Water Transport: Rivers and Seas 🌊
Rivers provided a steady supply of drinking water and made land fertile for growing crops. But more importantly, they made transportation easier. People living on river banks discovered they could float things in water—it was found easier than transporting on land .
Milestones in Water Transport:
D. Roads and Highways 🛣️
The Romans recognized the importance of good roads for extending and maintaining their empire. They developed an extensive network of Roman roads that connected their vast territories .
During the Industrial Revolution, John Loudon McAdam (1756-1836) designed the first modern highways using inexpensive paving material of soil and stone aggregate—this came to be known as macadam roads. These roads were embanked a few feet higher than the surrounding terrain to allow water to drain away from the surface .
E. Railways and Steam Power 🚂
The Industrial Revolution brought the steam engine, which revolutionized transport. Railways emerged as a powerful mode of transport, enabling mass movement of goods and people across long distances at unprecedented speeds .
F. Air and Space Travel ✈️
The 20th century saw the development of aircraft, beginning with the Wright brothers' first flight in 1903. The first commercial jet airliner was the British De Havilland Comet, marking the beginning of the Jet Age—a period of relatively cheap and fast international travel .
Space Exploration Milestones:
9.1.3 Transport in India: Historical Context
India has a rich transport heritage:
Indus Valley Civilization (c. 2600 BC) had the first canal irrigation system in the world
Ancient trade routes connected India with Central Asia, the Middle East, and Rome
The Grand Trunk Road, one of Asia's oldest and longest major roads, connected East Asia with West Asia
9.1.4 Pedagogical Implications
| Teaching Strategy | Description | PSTET Focus |
|---|---|---|
| Timeline Creation | Students create illustrated timelines of transport evolution | Visual learning, sequencing |
| "Then and Now" Comparison | Compare ancient and modern transport methods | Critical thinking |
| Local History Project | Research local transport history (bullock carts, tongas, etc.) | Connecting to community |
| Role Play | Students role-play as explorers using different transport modes | Engaging multiple intelligences |
Section 9.2: Measurement: Standard and Non-standard Units 📐
Introduction
Measurement is the process of determining the size, length, or amount of something. In ancient times, people used body parts for informal measurement, but these varied from person to person. This led to the development of standard units that are the same for everyone, everywhere .
9.2.1 Types of Measurement Units
Table 9.2: Standard vs. Non-standard Units
| Aspect | Non-standard Units | Standard Units |
|---|---|---|
| Definition | Units that vary from person to person; not fixed | Units with fixed, universally accepted values |
| Accuracy | Approximate; varies with individual | Precise; same for everyone |
| Examples | Handspan, cubit, footspan, pace, arm span | Metre, centimetre, kilometre, inch, foot |
| When Used | Introduction to measurement (young learners); rough estimates | Scientific work, trade, construction, formal measurements |
| Advantage | Easy to understand; no tools needed | Consistent, accurate, universally understood |
9.2.2 Non-standard Units of Measurement
Non-standard units are often used with young learners to introduce them to the concept of measurement without using scales. The objective is to focus the child on concepts like longer, shorter, heavier, lighter .
A. Handspan ✋
Definition: The distance between the tips of the thumb and the tip of the little finger on an open palm .
Uses: Can be used to measure small objects like books, water bottles, or the width of a table.
Limitation: Different people have different hand sizes—a child's handspan is smaller than an adult's.
📝 PSTET Note: Handspan measurement is not accurate for longer distances like the distance from school to home .
B. Cubit 💪
Definition: The length from the elbow to the tip of the middle finger .
Historical Significance: The cubit was used in ancient civilizations, including Egypt, for construction (e.g., building pyramids).
Uses: Can be used to measure objects like cloth, tables, beds, and chairs.
Limitation: Cannot be used for very long distances or large objects .
C. Footspan 👣
Definition: The length of a person's foot from heel to toe .
Uses: Can be used to measure the length of a room or floor.
Limitation: Very time-consuming for large areas; varies from person to person .
D. Pace (Stride) 🚶
Definition: The length of a single step while walking naturally. Pace measurement is taken by placing the right foot forward followed by the left foot .
Uses: Can be used to measure longer distances like the distance from school to home.
Advantage: Footsteps can be counted easily for longer distances.
Limitation: If there is a change in the length of the pace, it can lead to incorrect calculation .
E. Arm Span (Wingspan) 🦅
Definition: The physical length measured from one end of an individual's arms (measured at the fingertips) to the other when lifted parallel to the ground at shoulder height .
Uses: Measuring length of fabric, estimating height (arm span roughly equals height in many people).
9.2.3 Standard Units of Measurement
Standard units are what we usually use to measure things like weight, length, and volume. They are common units of measurement such as inches, pounds, and pints (in the Imperial system) or metres, kilograms, and litres (in the Metric system) .
A. The International System of Units (SI)
The SI system (Système International d'Unités) is the modern form of the metric system and is used by most countries worldwide .
Seven Base SI Units:
| Quantity | Unit | Symbol |
|---|---|---|
| Length | metre | m |
| Mass | kilogram | kg |
| Time | second | s |
| Electric current | ampere | A |
| Temperature | kelvin | K |
| Amount of substance | mole | mol |
| Luminous intensity | candela | cd |
B. Units of Length
SI Unit of Length: The metre (m)
Other Units of Length:
| Unit | Symbol | Relation to Metre |
|---|---|---|
| Kilometre | km | 1 km = 1000 m |
| Hectometre | hm | 1 hm = 100 m |
| Decametre | dam | 1 dam = 10 m |
| Metre | m | 1 m (base unit) |
| Decimetre | dm | 1 dm = 0.1 m |
| Centimetre | cm | 1 cm = 0.01 m |
| Millimetre | mm | 1 mm = 0.001 m |
Conversion Chart:
1000 m = 1 kilometre (km) 100 m = 1 hectometre (hm) 10 m = 1 decametre (dam) 1 m = 10 dm = 100 cm = 1000 mm 1 cm = 10 mm
C. When to Use Different Units
9.2.4 Metric System vs. Imperial System
| System | Used In | Length Units | Mass Units | Volume Units |
|---|---|---|---|---|
| Metric (SI) | Most countries worldwide | metre, centimetre, kilometre | gram, kilogram | litre, millilitre |
| Imperial/US Customary | USA, UK (partially) | inch, foot, yard, mile | pound, ounce | pint, gallon, cup |
Conversion Examples:
9.2.5 Pedagogical Implications
Section 9.3: Correct Way of Measuring Length 📏
Introduction
Measuring length accurately requires proper technique. Whether using a ruler, measuring tape, or metre stick, following correct procedures ensures that measurements are reliable and error-free .
9.3.1 Tools for Measuring Length
9.3.2 Steps for Correct Measurement Using a Ruler
A. Step 1: Position the Ruler Correctly 📏
| Do's | Don'ts |
|---|---|
| ✅ Place the ruler parallel to the length being measured | ❌ Don't let the ruler be at an angle |
| ✅ Ensure the ruler lies flat against the object | ❌ Don't hold it above the object |
| ✅ The object and ruler should be in contact | ❌ Don't measure from the edge of the ruler |
Why: If the ruler is not parallel to the object, the measurement will be longer than the actual length .
B. Step 2: Align with Zero Marker
| Do's | Don'ts |
|---|---|
| ✅ Align one end of the object with the zero mark on the ruler | ❌ Don't align with the edge of the ruler (it may be worn) |
| ✅ Check that the object is exactly at zero | ❌ Don't measure from 1 cm and subtract later (prone to error) |
Example: If Nader aligns his pencil with the 12 cm mark instead of zero, and the other end reaches 2.8 cm, he might incorrectly read 2.8 cm instead of calculating 12 - 2.8 = 9.2 cm .
C. Step 3: Read the Measurement Correctly 👁️
| Do's | Don'ts |
|---|---|
| ✅ Look straight at the mark (avoid parallax error) | ❌ Don't look from an angle |
| ✅ Read the value at the exact end of the object | ❌ Don't estimate beyond the ruler's resolution |
| ✅ For partial marks, count the smaller divisions | ❌ Don't round arbitrarily |
Understanding Resolution:
Rulers typically have marks at every millimetre
This means they can measure to the nearest millimetre (0.1 cm)
Between two centimetre marks, there are usually 10 equal divisions—each representing 1 mm
D. Step 4: Measure Curved Objects
For curved objects, a straight ruler cannot be used directly because it can never be parallel to the full length of a curved line. If you try to measure a curved line with a straight ruler, the measurement will be shorter than the actual length .
Solution: Use a flexible measuring tape or a thread that can follow the curve, then measure the thread against a ruler.
9.3.3 Common Mistakes in Measuring Length
Table 9.3: Measurement Errors and Corrections
9.3.4 Measuring Longer Distances (More Than One Ruler)
When a length is longer than a single ruler, multiple rulers can be used. The correct method:
Place the first ruler with its zero at the start of the object
Note the measurement at the end of the first ruler (e.g., 12.0 cm)
Place the second ruler with its zero aligned exactly with the 12.0 cm mark of the first ruler
Read the measurement where the object ends on the second ruler
Add the two measurements: 12.0 cm + (reading on second ruler)
Common Mistake: Leaving a gap between the rulers—this makes the measurement shorter than actual.
9.3.5 Specialized Tools for Very Small Lengths
For lengths on the order of millimetres, a micrometer is used. It measures with a precision of about one-millionth of a metre (one micrometre) .
Example: Measuring the thickness of a wire—a micrometer would give a more accurate reading than a metre ruler .
9.3.6 Pedagogical Implications
| Teaching Strategy | Description | PSTET Focus |
|---|---|---|
| "Mistake Detective" | Show incorrect measurements; students identify errors | Critical thinking |
| Hands-on Practice | Students measure various classroom objects | Skill development |
| Peer Checking | Students measure same object and compare results | Collaboration, accuracy awareness |
| Recording Measurements | Practice writing measurements with correct units (cm, mm) | Communication skills |
Section 9.4: Types of Motion (Rectilinear, Circular, Periodic) 🔄
Introduction
Motion is a change in the position of an object with time. Different objects move in different ways. By observing how objects move, we can classify motion into various types .
9.4.1 Classification of Motion
Table 9.4: Types of Motion with Examples
9.4.2 Detailed Study of Each Motion Type
A. Rectilinear Motion (Straight Line Motion)
Definition: An object is said to have rectilinear motion if it moves from one point to another in a straight line .
Characteristics:
Path is a straight line
Direction does not change
Also called linear motion
Examples:
The needle of a sewing machine moving up and down (though it's oscillatory, its path is straight)
A falling stone (ignoring air resistance)
A train on straight tracks
B. Circular Motion
Definition: An object is said to possess circular motion if it moves in such a way that its distance from a fixed point always remains constant .
Characteristics:
Path is a circle
Distance from centre (radius) remains constant
Direction changes continuously
Examples:
Movement of the blades of a fan—distance between blades and fan head remains same
Motion of Earth around the Sun (approximately circular)
Hands of a clock moving around the dial
Note: When an object moves on its own axis (like Earth rotating), it is called rotational motion. In circular motion, the object moves around an external centre .
C. Periodic Motion
Definition: An object is said to possess periodic motion if it moves in such a way that it repeats its motion after a certain fixed interval of time .
Characteristics:
Motion repeats after regular time intervals
The fixed time interval is called the period
Can be along any path (straight, circular, or other)
Examples:
Rotation of Earth (24-hour period)
Revolution of Moon around Earth
9.4.3 Other Types of Motion (Extended Knowledge)
For advanced understanding (beyond Class 6 level), there are additional types of motion:
9.4.4 Motion Comparison Chart
Table 9.5: Comparing Different Motion Types
| Feature | Rectilinear | Circular | Periodic | Oscillatory |
|---|---|---|---|---|
| Path | Straight line | Circle | Any path (repeating) | To and fro |
| Direction | Constant | Continuously changing | May change or remain same | Reverses |
| Time Repetition | Not necessarily | Not necessarily | Yes, fixed interval | Yes |
| Example | Train on straight track | Merry-go-round | Pendulum | Swing |
9.4.5 Motion in Daily Life: Recognizing Multiple Motions
Many objects show more than one type of motion simultaneously:
Example 1: A Moving Bicycle
Wheels: Circular motion (rotating)
Bicycle overall: Rectilinear motion (moving forward)
Pedals: Circular motion around the crank
Example 2: Earth
Rotation on axis: Rotational motion
Revolution around Sun: Circular motion (approximately)
Both motions are periodic (regular intervals)
Example 3: A Swing
Motion to and fro: Oscillatory motion
Repeats after fixed time: Periodic motion
9.4.6 Pedagogical Implications
| Teaching Strategy | Description | PSTET Focus |
|---|---|---|
| "Motion Hunt" | Students find and classify motions around them | Observation skills |
| Demonstration | Show different motions using toys (ball, fan, pendulum) | Visual learning |
| Body Motions | Students demonstrate motions with their bodies (walk straight, swing arms, spin) | Kinesthetic learning |
| Video Clips | Show videos of different motions (sports, machines, nature) | Engaging multiple senses |
| Create a "Motion Wheel" | Chart with examples of each motion type | Creative reinforcement |
Chapter Summary: Key Points for Revision 📝
Quick Revision Table
Practice Zone: PSTET-Style Questions 🎯
Content-Based MCQs
Q1. The invention of the wheel occurred around:
a) 10,000 BC
b) 3500 BC
c) 1000 BC
d) 500 AD
Q2. Which of the following is a non-standard unit of measurement?
a) Metre
b) Centimetre
c) Handspan
d) Kilometre
Q3. The SI unit of length is:
a) Centimetre
b) Kilometre
c) Metre
d) Foot
Q4. 5 kilometres is equal to:
a) 50 metres
b) 500 metres
c) 5000 metres
d) 50,000 metres
Q5. Which of the following is an example of rectilinear motion?
a) Motion of a fan blade
b) Motion of a car on a straight road
c) Motion of a merry-go-round
d) Motion of a clock's pendulum
Q6. The motion that repeats after a fixed interval of time is called:
a) Circular motion
b) Rectilinear motion
c) Periodic motion
d) Random motion
Q7. Which tool would be most appropriate to measure the thickness of a wire?
a) Metre ruler
b) Measuring tape
c) Micrometer
d) Trundle wheel
Q8. While measuring length with a ruler, the ruler should be:
a) At an angle to the object
b) Parallel to the object
c) Perpendicular to the object
d) Held above the object
Q9. The distance from the elbow to the tip of the middle finger is called:
a) Handspan
b) Cubit
c) Footspan
d) Pace
Q10. Which of the following shows combination motion (more than one type)?
a) Stationary fan
b) Moving bicycle
c) Pendulum at rest
d) Book on table
Pedagogical MCQs
Q11. A teacher asks students to measure the length of their desk using their handspan. This activity introduces:
a) Standard units
b) Non-standard units
c) Circular motion
d) Periodic motion
Q12. To demonstrate that different people have different handspans, the best activity would be:
a) Show a video about measurement
b) Have all students measure the same object with their handspan and compare results
c) Read from textbook
d) Draw handspan diagrams on board
Q13. A student places the ruler at an angle while measuring a pencil. The measurement will be:
a) Accurate
b) Shorter than actual
c) Longer than actual
d) Unaffected
Q14. While teaching types of motion, showing a pendulum clock demonstrates:
a) Rectilinear motion only
b) Circular motion only
c) Periodic motion
d) Random motion
Q15. The most effective way to teach the concept of "standard units" is to:
a) Give a lecture on SI units
b) First have students measure with non-standard units (find inconsistencies), then introduce standard units
c) Show a video about measurement
d) Have students memorize conversion tables
Answer Key with Explanations
Pedagogical Reflection for Teachers 🤔
Think-Pair-Share Activity:
Think: How would you explain to your students why we cannot use handspan as a standard unit for measuring length across the world?
Pair: Discuss with a colleague how you would set up a "Measurement Station" in your classroom with different tools (rulers, tapes, metre sticks) for students to practice.
Share: Design a 15-minute activity to teach the three types of motion using objects easily available in the classroom.
NCERT Textbook Linkages 📚
| Class | Chapter | Topic |
|---|---|---|
| Class 6 | Chapter 10 | Motion and Measurement of Distances |
| Class 7 | Chapter 13 | Motion and Time |
| Class 9 | Chapter 8 | Motion |
Chapter End Notes
Key Terminology Glossary
Quick Tips for PSTET Aspirants ⚡
✅ Memorize with Mnemonics:
Transport Evolution: "Walking Animals Wheel Ships Roads Railways Airplanes Space"
Walking, Animal transport, Wheel, Ships, Roman roads, Railways, Airplanes, Space
Non-standard Units: "Hands Carry Feet People" = Handspan, Cubit, Footspan, Pace
Length Units (small to large): "My Cat Dances Merrily During Happy Karaoke"
Mm, Cm, Dm, M, Dam, Hm, Km
Motion Types: "Raj Cooks Pasta" = Rectilinear, Circular, Periodic
✅ Common Exam Traps:
Handspan vs. Cubit: Handspan = thumb to little finger; Cubit = elbow to fingertip
Metre vs. Kilometre: Use metres for room length; use kilometres for city distances
Circular vs. Rotational: Circular = around external centre; Rotational = around own axis
Periodic vs. Oscillatory: All oscillatory motion is periodic, but not all periodic motion is oscillatory (e.g., Earth's revolution is periodic but not oscillatory)
✅ Important Facts:
Roman roads: First major road network
1 km = 1000 m, 1 m = 100 cm, 1 cm = 10 mm
Parallax error occurs when viewing from an angle
Answers to "Check Your Understanding"
[To be filled by student]
📝 Note for Self-Study: After completing this chapter, ensure you can:
List 5 major developments in the history of transport with approximate time periods
Name 5 non-standard units of measurement and explain their limitations
Write the SI unit of length and its conversions (km, m, cm, mm)
Describe the correct procedure for measuring length with a ruler
Identify 3 common mistakes in measurement and how to avoid them
Define rectilinear, circular, and periodic motion with 3 examples each
Differentiate between circular and rotational motion
Give an example of an object showing combination motion
End of Chapter 9
Next Chapter: Chapter 10 - Force and Pressure
Topics Covered: Push and Pull, Effects of Force, Types of Forces, Pressure
