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Chapter 5. Measurement of Length and Motion

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).

Unit	Relationship
1 kilometre	1000 metres
1 metre	100 centimetres
1 centimetre	10 millimetres

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.

Chapter 5. Measurement of Length and Motion

NCERT Text Book Questions With Answers

Chapter 5. Measurement of Length and Motion

The NCERT Textbook Exercise is designed to help students revise all the important concepts covered in this chapter. The following solutions are prepared according to the latest NCERT Curiosity textbook and CBSE guidelines. Students should first attempt the questions independently and then compare their answers with the solutions provided below.

NCERT Textbook Exercise

Question 1. Fill in the blanks.

(i) The SI unit of length is metre (m).

(ii) The position of an object is described with respect to a reference point.

(iii) Motion along a straight path is called linear motion.

(iv) Motion that repeats itself after equal intervals of time is called periodic motion.

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Question 2. State whether the following statements are True (T) or False (F).

(i) Handspan is a standard unit of length.

Answer: False

(ii) A measuring tape can be used to measure curved objects.

Answer: True

(iii) Every moving object always travels in a straight line.

Answer: False

(iv) The Earth rotates about its own axis.

Answer: True

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Question 3. Match the following.

Column A	Column B
Metre	SI unit of length
Measuring Tape	Measures curved objects
Circular Motion	Motion along a circular path
Oscillatory Motion	To-and-fro motion

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Question 4. Why were body parts such as handspan and footstep not considered reliable units of measurement?

Answer:

Body-part measurements were not reliable because the size of hands, feet, and arms differs from person to person. As a result, different people obtained different measurements for the same object. Therefore, standard units of measurement were introduced to ensure accuracy and uniformity.

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Question 5. Why is the SI system of units important?

Answer:

The SI system provides standard units that are accepted throughout the world. It ensures that measurements are accurate, uniform, and easily understood everywhere, making scientific work, trade, engineering, and communication more reliable.

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Question 6. How can you measure the length of a curved line?

Answer:

Place a thread carefully along the curved line. Mark the two ends of the thread, straighten it, and measure its length using a ruler or metre scale. A flexible measuring tape can also be used for measuring curved objects.

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Question 7. What is meant by a reference point? Explain with an example.

Answer:

A reference point is a fixed object or position used to describe the location or motion of another object.

For example, a car may be moving with respect to a tree beside the road, but a passenger sitting inside the car is at rest with respect to the car.

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Question 8. Differentiate between rest and motion.

Answer:

Rest	Motion
The position of an object does not change with time with respect to a reference point.	The position of an object changes with time with respect to a reference point.
Example: A book lying on a table.	Example: A moving bicycle.

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Question 9. Explain the different types of motion with one example each.

Answer:

• Linear Motion: Motion along a straight line. Example: A train moving on a straight track.
• Circular Motion: Motion along a circular path. Example: The blades of a ceiling fan.
• Oscillatory Motion: To-and-fro motion about a fixed position. Example: A swinging pendulum.

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Question 10. Why should your eye be placed vertically above the scale while taking a measurement?

Answer:

The eye should be placed vertically above the marking to avoid parallax error. Looking at the scale from an angle may result in an incorrect reading and reduce the accuracy of the measurement.

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Question 11. The zero mark of a ruler is damaged. Can the ruler still be used for measurement? Explain.

Answer:

Yes. Place one end of the object at another clear marking on the ruler instead of the damaged zero mark. Note the initial and final readings, then subtract the initial reading from the final reading to obtain the correct length of the object.

Chapter 5. Measurement of Length and Motion

Extra Questions Examination Based

Chapter 5. Measurement of Length and Motion

The following important questions are prepared according to the latest CBSE pattern and the NCERT Curiosity textbook. These questions cover all the important concepts of the chapter and help students improve their conceptual understanding and examination skills.

Important Questions with Answers

Students are advised to answer these questions on their own before referring to the solutions given below.

1 Mark Questions

Question 1. What is the SI unit of length?

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

Question 2. Name the instrument used to measure the length of a curved object.

Answer: A measuring tape or a thread.

Question 3. What is a reference point?

Answer: A fixed object or position used to describe the location or motion of another object.

Question 4. Define motion.

Answer: Motion is the change in the position of an object with time with respect to a reference point.

Question 5. What is meant by rest?

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

Question 6. Name the three main types of motion discussed in this chapter.

Answer: Linear motion, circular motion, and oscillatory motion.

Question 7. Which measuring instrument is used to measure the length of a table?

Answer: A metre scale.

Question 8. What is periodic motion?

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

Question 9. Why is a standard unit of measurement necessary?

Answer: It provides uniform and accurate measurements everywhere.

Question 10. What is parallax error?

Answer: It is the error caused when the scale is read from an angle instead of vertically above the marking.

2 Marks Questions

Question 1. Why were body-part measurements replaced by standard units?

Answer:

• Body parts differ from person to person.
• Measurements obtained were not accurate.
• Standard units provide uniform and reliable measurements.

Question 2. Write the relationships among kilometre, metre, centimetre, and millimetre.

Answer:

• 1 km = 1000 m
• 1 m = 100 cm
• 1 cm = 10 mm

Question 3. How can a damaged ruler still be used to measure length?

Answer:

• Start measuring from another clear marking.
• Record the initial and final readings.
• Subtract the initial reading from the final reading.

Question 4. How is the length of a curved line measured?

Answer:

• Place a thread along the curved line.
• Straighten the thread.
• Measure its length using a ruler.

Question 5. Differentiate between rest and motion.

Answer:

• An object at rest does not change its position with time.
• An object in motion changes its position with time.
• Both depend on the chosen reference point.

3 Marks Questions

Question 1. Explain the correct method of measuring the length of an object.

Answer:

• Place the ruler along the object.
• Align the zero mark with one end.
• Keep the eye vertically above the scale.
• Read the other end carefully.
• Avoid parallax error.

Question 2. Explain linear, circular, and oscillatory motion with examples.

Answer:

• Linear Motion: Motion along a straight line. Example: A train moving on a straight track.
• Circular Motion: Motion along a circular path. Example: A ceiling fan.
• Oscillatory Motion: To-and-fro motion about a fixed position. Example: A swinging pendulum.

Question 3. Why is a reference point important in describing motion?

Answer:

• It helps determine the position of an object.
• It helps decide whether an object is at rest or in motion.
• Without a reference point, motion cannot be described accurately.

Question 4. Describe the uses of different measuring instruments.

Answer:

• Ruler – Small objects.
• Metre scale – Larger objects.
• Measuring tape – Curved objects and long distances.

Question 5. Explain periodic motion with suitable examples.

Answer:

• Periodic motion repeats after equal intervals of time.
• A swinging pendulum is an example.
• The rotation of the hands of a clock is another example.
• The motion of a merry-go-round is also periodic.

Long Answer Questions

Question 1. Explain the importance of standard units of measurement.

Answer:

Standard units ensure that measurements remain the same everywhere in the world. They eliminate confusion caused by body-part measurements and provide accurate, reliable, and uniform results. Standard units are essential in science, engineering, construction, medicine, sports, trade, and everyday life. The International System of Units (SI) is accepted worldwide because it provides consistency in measurement.

Question 2. Describe the different measuring instruments and their uses.

Answer:

Different measuring instruments are used according to the size and shape of the object. A ruler is suitable for measuring small objects such as pencils and notebooks. A metre scale is used for larger objects such as tables and doors. A measuring tape is flexible and is useful for measuring curved objects, body measurements, cloth, and long distances. Choosing the correct instrument ensures accurate measurements.

Question 3. Explain the concept of rest and motion with suitable examples.

Answer:

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, it is said to be in motion. For example, a book placed on a table is at rest with respect to the table, whereas a moving bicycle is in motion with respect to the road. Rest and motion always depend on the selected reference point.

Question 4. Describe the different types of motion with examples.

Answer:

Linear motion occurs along a straight path, such as a train moving on a straight railway track. Circular motion occurs along a circular path, such as the blades of a fan or a merry-go-round. Oscillatory motion is the repeated to-and-fro movement of an object about a fixed position, such as a pendulum or a swing. Some of these motions repeat regularly and are called periodic motions.

Question 5. Explain the precautions to be taken while measuring length.

Answer:

The measuring scale should be placed exactly along the object. The zero mark must coincide with one end of the object. The eye should be positioned vertically above the reading to avoid parallax error. If the zero mark is damaged, another clear marking should be used, and the initial reading should be subtracted from the final reading. Proper measuring instruments should always be selected according to the object being measured.

Chapter 5. Measurement of Length and Motion

40 Important MCQs with Answers

Chapter 5. Measurement of Length and Motion

The following Multiple Choice Questions (MCQs) are prepared according to the latest NCERT Curiosity textbook and CBSE examination pattern. These questions cover all the important concepts of the chapter and help students strengthen their conceptual understanding and examination skills.

40 Important MCQs with Answer Key

Question 1. What is the SI unit of length?

• (A) Centimetre
• (B) Metre
• (C) Kilometre
• (D) Millimetre

Question 2. Which instrument is best suited to measure the length of a classroom?

• (A) Ruler
• (B) Measuring Tape
• (C) Vernier Calipers
• (D) Compass

Question 3. One metre is equal to _____ centimetres.

• (A) 10
• (B) 100
• (C) 1000
• (D) 10000

Question 4. One kilometre is equal to _____ metres.

• (A) 10
• (B) 100
• (C) 1000
• (D) 10000

Question 5. Which of the following is a standard unit of length?

• (A) Handspan
• (B) Cubit
• (C) Metre
• (D) Footstep

Question 6. Which instrument is most suitable for measuring the length of a pencil?

• (A) Measuring Tape
• (B) Ruler
• (C) Metre Scale
• (D) Odometer

Question 7. Curved lengths are generally measured using a _____.

• (A) Thread
• (B) Brick
• (C) Compass
• (D) Thermometer

Question 8. Reading a scale from an angle causes _____.

• (A) Rotation
• (B) Oscillation
• (C) Parallax Error
• (D) Circular Motion

Question 9. Which unit is smaller than a centimetre?

• (A) Kilometre
• (B) Metre
• (C) Millimetre
• (D) Foot

Question 10. One centimetre is equal to _____ millimetres.

• (A) 2
• (B) 5
• (C) 10
• (D) 100

Question 11. The position of an object is described with respect to a _____.

• (A) Magnet
• (B) Reference Point
• (C) Scale
• (D) Clock

Question 12. An object is said to be in motion when its _____ changes with time.

• (A) Colour
• (B) Shape
• (C) Position
• (D) Size

Question 13. Motion along a straight path is called _____.

• (A) Circular Motion
• (B) Oscillatory Motion
• (C) Linear Motion
• (D) Random Motion

Question 14. The motion of a ceiling fan is an example of _____.

• (A) Linear Motion
• (B) Circular Motion
• (C) Oscillatory Motion
• (D) Rectilinear Motion

Question 15. A swinging pendulum shows _____.

• (A) Circular Motion
• (B) Linear Motion
• (C) Oscillatory Motion
• (D) Random Motion

Question 16. Motion that repeats after equal intervals of time is called _____.

• (A) Random Motion
• (B) Zigzag Motion
• (C) Periodic Motion
• (D) Linear Motion

Question 17. Which of the following is an example of linear motion?

• (A) Merry-go-round
• (B) Swing
• (C) Train moving on a straight track
• (D) Rotating fan

Question 18. Which of the following is an example of circular motion?

• (A) Falling stone
• (B) Rotating wheel
• (C) Walking person
• (D) Moving lift

Question 19. Which of the following is an example of oscillatory motion?

• (A) Clock pendulum
• (B) Running car
• (C) Flying bird
• (D) Bullet train

Question 20. Which of the following is periodic?

• (A) Swing
• (B) Earth rotating on its axis
• (C) Hands of a clock
• (D) All of these

Question 21. Which ancient Indian unit of length is mentioned in the chapter?

• (A) Mile
• (B) Angula
• (C) Yard
• (D) Inch

Question 22. Which ancient unit represented a long distance?

• (A) Millimetre
• (B) Yojana
• (C) Centimetre
• (D) Inch

Question 23. A measuring tape is generally made of _____.

• (A) Flexible material
• (B) Glass
• (C) Wood only
• (D) Stone

Question 24. Which instrument is suitable for measuring body measurements?

• (A) Metre Scale
• (B) Measuring Tape
• (C) Ruler
• (D) Divider

Question 25. If the zero mark of a ruler is damaged, you should _____.

• (A) Throw away the ruler
• (B) Begin from another marking
• (C) Guess the length
• (D) Use only the damaged end

Question 26. Accurate measurements are important in _____.

• (A) Construction
• (B) Science
• (C) Engineering
• (D) All of these

Question 27. Which error is avoided by keeping the eye vertically above the scale?

• (A) Human Error
• (B) Instrument Error
• (C) Parallax Error
• (D) Random Error

Question 28. The SI system is accepted _____.

• (A) Only in India
• (B) Only in Asia
• (C) Worldwide
• (D) Only in Europe

Question 29. Which unit is most suitable for measuring the distance between two cities?

• (A) Millimetre
• (B) Centimetre
• (C) Metre
• (D) Kilometre

Question 30. Which object is generally measured using a metre scale?

• (A) Pencil
• (B) Table
• (C) Needle
• (D) Coin

Question 31. Which statement is correct?

• (A) Motion depends on a reference point.
• (B) Motion never changes.
• (C) Reference points are unnecessary.
• (D) All objects are always at rest.

Question 32. Which object can be at rest with respect to one object and in motion with respect to another?

• (A) A passenger inside a moving bus
• (B) A tree
• (C) A building
• (D) A mountain

Question 33. The movement of a merry-go-round is _____.

• (A) Linear Motion
• (B) Circular Motion
• (C) Oscillatory Motion
• (D) Random Motion

Question 34. Which of the following is NOT a standard unit?

• (A) Metre
• (B) Kilometre
• (C) Handspan
• (D) Centimetre

Question 35. Measurement helps us to _____.

• (A) Compare objects accurately
• (B) Guess distances
• (C) Change motion
• (D) Stop movement

Question 36. Which of the following is measured in kilometres?

• (A) Width of a notebook
• (B) Height of a chair
• (C) Distance between two towns
• (D) Length of a pen

Question 37. Which type of motion is shown by the Earth revolving around the Sun?

• (A) Circular Motion
• (B) Linear Motion
• (C) Oscillatory Motion
• (D) Random Motion

Question 38. Which of the following is NOT a measuring instrument?

• (A) Ruler
• (B) Measuring Tape
• (C) Metre Scale
• (D) Compass

Question 39. Which motion is repeated again and again after equal intervals?

• (A) Random Motion
• (B) Periodic Motion
• (C) Zigzag Motion
• (D) Irregular Motion

Question 40. Which statement about measurement is correct?

• (A) Standard units make measurements uniform.
• (B) Handspan is more accurate than a metre.
• (C) Body-part measurements are accepted worldwide.
• (D) Standard units are unnecessary.

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Answer Key

1. B
2. B
3. B
4. C
5. C
6. B
7. A
8. C
9. C
10. C
11. B
12. C
13. C
14. B
15. C
16. C
17. C
18. B
19. A
20. D
21. B
22. B
23. A
24. B
25. B
26. D
27. C
28. C
29. D
30. B
31. A
32. A
33. B
34. C
35. A
36. C
37. A
38. D
39. B
40. A