Class 6 Science Chapter 5 A Journey Through States of Water – easy notes, concepts, NCERT book solutions, important questions, worksheet and answers. Learn about the different states of water, changes of state, evaporation, condensation and the water cycle in simple language.
Class 6 Science
Chapter 5: Measurement of Length and Motion
Color Notes • Easy Concepts • Textbook Questions & Solutions
📘 Chapter Overview
In this chapter we learn:
- How to measure length correctly.
- Why standard units are needed.
- SI units of length.
- How to use a scale and measuring tape.
- How to measure curved lengths.
- What a reference point is.
- How to identify motion and rest.
- Different types of motion.
🌟 Important Concepts
1. Measurement
Measurement tells us how much of a quantity is present by comparing it with a standard unit.
A measurement has two parts:
Number + Unit
Example: 13 cm = 13 is the number and cm is the unit.
2. Why do we need standard units?
Body parts such as handspan, foot and finger width are different for different people. Therefore, they may give different measurements. Standard units give the same measurement to everyone.
3. SI Units
The International System of Units is called the SI system.
| Quantity | SI Unit | Symbol |
|---|---|---|
| Length | metre | m |
1 km = 1000 m
1 m = 100 cm
1 cm = 10 mm
1 m = 100 cm
1 cm = 10 mm
4. Smaller and Larger Units
| Unit | Use |
|---|---|
| km | Very large distances |
| m | Medium lengths |
| cm | Small lengths |
| mm | Very small lengths |
5. Correct Way to Measure Length
- Place the scale along the length of the object.
- Keep the scale in contact with the object.
- Keep your eye directly above the marking being read.
- Always write the unit with the measurement.
6. Broken Zero Mark
If the zero end of a scale is broken, start from another clear marking and subtract the first reading from the final reading.
Length = Final reading − Initial reading
7. Measuring Curved Length
A curved line can be measured using a flexible measuring tape or a thread. Straighten the thread and measure it using a scale.
8. Reference Point
A fixed object or point with respect to which distance or position is stated is called a reference point.
9. Motion
An object is in motion if its position changes with respect to a reference point with time.
10. Rest
An object is at rest if its position does not change with respect to a reference point with time.
🏃 Types of Motion
🔵
Linear Motion
Movement along a straight line.
Linear Motion
Movement along a straight line.
🟢
Circular Motion
Movement along a circular path.
Circular Motion
Movement along a circular path.
🟣
Oscillatory Motion
To-and-fro movement about a fixed position.
Oscillatory Motion
To-and-fro movement about a fixed position.
Examples:
- Car moving on a straight road → Linear motion
- Blades of a fan → Circular motion
- Swing moving to and fro → Oscillatory motion
Periodic motion: If an object repeats its path after a fixed interval of time, its motion is called periodic motion.
🔑 Keywords
Length Measurement SI Unit metre kilometre centimetre millimetre Reference Point Motion Linear Motion Circular Motion Oscillatory Motion Periodic Motion⚡ Quick Revision
- SI unit of length is metre (m).
- 1 km = 1000 m.
- 1 m = 100 cm.
- 1 cm = 10 mm.
- A measurement has a number and a unit.
- A fixed point used to describe position is a reference point.
- Change of position with time means motion.
- Straight-line path → linear motion.
- Circular path → circular motion.
- To-and-fro motion → oscillatory motion.
🔬 Important Activities
Activity 5.1: Let us measure
Select objects such as a comb, pen, pencil and eraser. Measure their lengths using a metre scale and record the measurements.Activity 5.2: Let us explore
List five objects that are in motion and five objects that are at rest. Give a reason for each observation.Activity 5.3: Let us explore
Drop an eraser from a height and observe its path. Decide whether its motion is along a straight line.Activity 5.4: Let us investigate
Tie an eraser or potato to a thread and whirl it. Its motion is circular motion.Activity 5.5: Let us investigate
Move an eraser to one side and release it. Its to-and-fro movement is oscillatory motion.Activity 5.6: Let us investigate
A bent metal strip moving up and down demonstrates oscillatory motion.Activity 5.7: Let us identify
Observe motions in a children’s park and classify them as linear, circular or oscillatory.📚 Let Us Enhance Our Learning – Book Solutions
1. Some lengths are given in Column I of Table 5.5. Some units are given in Column II. Match the lengths with the units suitable for measuring those lengths.
| Column I | Correct Unit |
|---|---|
| Distance between Delhi and Lucknow | kilometre |
| Thickness of a coin | millimetre |
| Length of an eraser | centimetre |
| Length of school ground | metre |
Answer: Distance between Delhi and Lucknow – kilometre; Thickness of a coin – millimetre; Length of an eraser – centimetre; Length of school ground – metre.
2. Read the following statements and mark True (T) or False (F) against each.
(i) The motion of a car moving on a straight road is an example of linear motion. [ ]
(ii) Any object which is changing its position with respect to a reference point with time is said to be in motion. [ ]
(iii) 1 km = 100 cm [ ]
Answer:
(i) T
(ii) T
(iii) F
(i) T
(ii) T
(iii) F
3. Which of the following is not a standard unit of measuring length?
(i) millimetre (ii) centimetre (iii) kilometre (iv) handspan
Answer: (iv) handspan
4. Search for the different scales or measuring tapes at your home and school. Find out the smallest value that can be measured using each of these scales. Record your observations in a tabular form.
| Measuring device | Smallest value |
|---|---|
| 15-cm ruler | 1 mm |
| Metre scale | Usually 1 mm |
| Measuring tape | Depends on its markings |
Answer: The smallest value depends on the markings of the measuring device. A common school ruler can measure up to 1 mm.
5. Suppose the distance between your school and home is 1.5 km. Express it in metres.
1 km = 1000 m
1.5 km = 1.5 × 1000 = 1500 m
1.5 km = 1.5 × 1000 = 1500 m
Answer: 1500 m
6. Take a tumbler or a bottle. Measure the length of the curved part of the base of glass or bottle and record it.
Answer: This is an activity-based question. Use a flexible measuring tape or thread to measure the curved part. The answer will depend on the tumbler or bottle used.
7. Measure the height of your friend and express it in (i) metres (ii) centimetres and (iii) millimetres.
Answer: This is an activity-based question. For example, if the height is 1.45 m:
(i) 1.45 m
(ii) 145 cm
(iii) 1450 mm
(i) 1.45 m
(ii) 145 cm
(iii) 1450 mm
8. You are given a coin. Estimate how many coins are required to be placed one after the other lengthwise, without leaving any gap between them, to cover the whole length of the chosen side of a notebook. Verify your estimate by measuring the same side of the notebook and the size of the coin using a 15-cm scale.
Answer: First estimate the number of coins. Then measure the notebook side and the diameter of the coin. Divide the notebook length by the coin size and compare the result with your estimate.
9. Give two examples each for linear, circular and oscillatory motion.
Answer:
Linear motion: A car moving on a straight road; a ball moving along a straight path.
Circular motion: Blades of a fan; a stone whirled with a string.
Oscillatory motion: A swing; a vibrating metal strip.
Linear motion: A car moving on a straight road; a ball moving along a straight path.
Circular motion: Blades of a fan; a stone whirled with a string.
Oscillatory motion: A swing; a vibrating metal strip.
10. Observe different objects around you. It is easier to express the lengths of some objects in mm, some in cm and some in m. Make a list of three objects in each category and enter them in the Table 5.6.
| Size | Objects |
|---|---|
| mm | Thickness of a coin, thickness of a sheet, thickness of a page |
| cm | Length of a pencil, length of an eraser, width of a notebook |
| m | Height of a door, length of a classroom, height of a person |
11. A rollercoaster track is made in the shape shown in Fig. 5.19. A ball starts from point A and escapes through point F. Identify the types of motion of the ball on the rollercoaster and corresponding portions of the track.
Answer: The ball can show different types of motion depending on the shape of the track. Along a straight portion it shows linear motion. Along a curved portion it follows a curved path; where the track forms a circular part, it shows circular motion. The exact portions are identified by observing the shape of Fig. 5.19.
🔎 Learning Further
1. Thickness of one page
Measure a large number of pages together, then divide the total thickness by the number of pages.
Measure a large number of pages together, then divide the total thickness by the number of pages.
2. Measuring leaves
Collect fallen leaves from the same tree. Measure their length and breadth and record the observations in a table.
Collect fallen leaves from the same tree. Measure their length and breadth and record the observations in a table.
Why can leaves from the same tree have different sizes?
Leaves may differ because of their age, position on the tree, amount of sunlight, water and other growing conditions.
Leaves may differ because of their age, position on the tree, amount of sunlight, water and other growing conditions.
📚 More Book Questions
12. Tasneem wants to make a metre scale by herself. She considers the following materials for it—plywood, paper, cloth, stretchable rubber and steel. Which of these should she not use and why?
Answer: She should not use paper, cloth and stretchable rubber because they can bend or change length easily. A scale should be made from a material that keeps its length and shape. Steel or suitable rigid plywood is more suitable.
13. Think, design and develop a card game on conversion of units of length to play with your friends.
Answer: This is a creative activity. Make cards containing values such as 2 m, 200 cm, 2000 mm and 0.002 km. Players match cards that represent the same length. The player making the most correct matches wins.
📏 Unit Conversion Tricks
km → m → cm → mm
To convert km to m: multiply by 1000.
Example: 2 km = 2000 m
Example: 2 km = 2000 m
To convert m to cm: multiply by 100.
Example: 3 m = 300 cm
Example: 3 m = 300 cm
To convert cm to mm: multiply by 10.
Example: 7 cm = 70 mm
Example: 7 cm = 70 mm
Remember: Moving from a larger unit to a smaller unit → multiply.
⚠️ Common Mistakes to Avoid
- Do not forget to write the unit.
- Do not keep your eye at an angle while reading a scale.
- Do not use handspan as a standard unit.
- Do not confuse metre and millimetre.
- Always choose a suitable measuring device.
- Motion depends on the reference point.
📝 Chapter Summary
- Measurement consists of a number and a unit.
- Standard units are needed for uniform measurements.
- The SI unit of length is metre.
- 1 km = 1000 m, 1 m = 100 cm and 1 cm = 10 mm.
- A reference point helps us describe position.
- An object whose position changes with time is in motion.
- Straight-line movement is linear motion.
- Circular-path movement is circular motion.
- To-and-fro movement is oscillatory motion.
- Repeated motion after a fixed interval is periodic motion.
Practice Class 6 Science Chapter 5
Looking for extra practice? Use the worksheet below to revise Chapter 5 with easy questions, extra practice questions and revision exercises.
Class 6 Science Chapter 5, A Journey Through States of Water, Class 6 Science notes, Class 6 Science solutions, NCERT Class 6 Science Chapter 5, Class 6 Science worksheet, water states, evaporation, condensation, water cycle, Class 6 Science questions and answers.