Chapter 5: Measurement of Length and Motion – Question and Answer
1. Match the lengths with suitable units (Table 5.5):
| Column I | Column II |
|---|---|
| Distance between Delhi and Lucknow | kilometre |
| Thickness of a coin | millimetre |
| Length of an eraser | centimetre |
| Length of school ground | metre |
2. True (T) or False (F):
- The motion of a car moving on a straight road is an example of linear motion. (T)
- Any object which is changing its position with respect to a reference point with time is said to be in motion. (T)
- 1 km = 100 cm (F)
3. Non-standard unit of measuring length:
(iv) handspan
4. Finding smallest values on scales or tapes:
Example table for observation:
| Measuring Device | Smallest Value Measured |
|---|---|
| Ruler (15 cm) | 1 mm |
| Tailor’s measuring tape | 1 mm |
| Carpenters’ steel scale | 1 mm |
5. Distance from school to home in metres:
1.5 km = 1.5×1000=1500 m1.5 \times 1000 = 1500 \, \text{m}
6. Measuring curved parts of a tumbler or bottle:
Use a thread to measure the curved part. Straighten the thread and measure its length using a scale.
7. Height measurement in various units:
- Height = 1.5 m
- (i) In metres: 1.5 m
- (ii) In centimetres: 1.5×100=150 cm1.5 \times 100 = 150 \, \text{cm}
- (iii) In millimetres: 150×10=1500 mm150 \times 10 = 1500 \, \text{mm}
8. Coins to cover a notebook side:
- Measure the length of the notebook side (e.g., 25 cm).
- Measure the length of a coin (e.g., 2.5 cm).
- Divide notebook length by coin length: 25 cm÷2.5 cm=10 coins25 \, \text{cm} \div 2.5 \, \text{cm} = 10 \, \text{coins}.
9. Examples of Motion:
| Type | Examples |
|---|---|
| Linear Motion | A car moving on a straight road, a train. |
| Circular Motion | A spinning wheel, a merry-go-round. |
| Oscillatory Motion | A swing, a pendulum. |
10. Objects and their measurement units:
| Size | Objects |
|---|---|
| mm | Thickness of a coin, wire, page |
| cm | Length of an eraser, a spoon, a leaf |
| m | Height of a door, width of a room |
11. Motion on Rollercoaster (Fig. 5.19):
- A to B, E to F: Linear motion.
- B to C, D to E: Circular motion.
- C to D: Oscillatory motion.
12. Measuring the thickness of a single page:
- Take a stack of 50 pages. Measure the total thickness using a ruler (e.g., 5 mm).
- Divide the total thickness by the number of pages:
Thickness of one page=5 mm÷50=0.1 mm\text{Thickness of one page} = 5 \, \text{mm} \div 50 = 0.1 \, \text{mm}.
13. Materials for a metre scale:
- Not suitable materials: Stretchable rubber (it stretches and gives inaccurate measurements).
- Preferred materials: Steel, plywood.
14. Old units of measurement:
Examples from elders:
- Handspan, foot-length, arm’s length (angula or balisht).
- Archaeological findings: Indus Valley rulers with standard units.
15. Conversion card game idea:
Create cards with length conversions:
- Front: “Convert 2.5 m to cm.”
- Back: “Answer: 2.5×100=250 cm2.5 \times 100 = 250 \, \text{cm}.”
This can help students practice.
16. Fun measuring method (Bicycle):
- Attach a strip to the spoke of the bicycle wheel. Count the clicks for the number of rotations.
- Measure the wheel’s circumference. Multiply by the number of rotations for the total distance.
17. Length and breadth of leaves (Table 5.7):
| S. no. | Name of Tree | Length of Leaf (cm) | Breadth of Leaf (cm) |
|---|---|---|---|
| 1 | Mango | 15 | 6 |
| 2 | Neem | 10 | 3 |
| 3 | Banana | 30 | 10 |
These answers cover the concepts of measurement of length and motion comprehensively while encouraging practical understanding. 😊
Question and Answer
1. What are the differences between a measuring rod and a flexible tape?
Answer:
- Measuring Rod: It is rigid and used for measuring straight objects like cloth or walls.
- Flexible Tape: It can bend and is suitable for measuring curved or irregular objects like a person’s body or the girth of a tree.
2. What did Deepa’s mother mean by “char angula”?
Answer:
“Char angula” refers to four finger widths, an informal unit of measurement traditionally used in India.
3. Why do different people get varying measurements using handspan?
Answer:
The size of handspans differs from person to person due to variations in hand size.
4. Why do we need standard units for measurement?
Answer:
Standard units ensure uniformity and consistency so that measurements remain the same irrespective of who measures or where it is measured.
5. What is the SI unit of length?
Answer:
The SI unit of length is the metre (m).
6. Convert the following:
- 5 km to metres
- 120 cm to metres
- 7 m to centimetres
Answer:
- 5 km = 5×1000=5000 m5 \times 1000 = 5000 \, \text{m}
- 120 cm = 120÷100=1.2 m120 \div 100 = 1.2 \, \text{m}
- 7 m = 7×100=700 cm7 \times 100 = 700 \, \text{cm}
7. How do visually challenged individuals measure lengths?
Answer:
They use scales with raised markings, which can be felt by touch.
8. How can you measure the length of a curved line?
Answer:
Use a flexible measuring tape or a thread. Place the thread along the curved line, then straighten the thread and measure its length using a scale.
9. What is a reference point?
Answer:
A reference point is a fixed location used to describe the position or movement of an object.
10. How can you measure the length of an object using a broken scale?
Answer:
Start measuring from a clear mark (e.g., 1 cm) instead of zero. Subtract this starting mark from the final reading to get the object’s length.
11. Write the types of motion with examples.
| Type of Motion | Examples |
|---|---|
| Linear Motion | Car moving on a straight road. |
| Circular Motion | A merry-go-round, whirling a stone. |
| Oscillatory Motion | A pendulum, a swing. |
12. How do kilometre stones help travellers?
Answer:
Kilometre stones indicate the distance from a reference point, such as a city, helping travellers track their journey progress.
13. What is the smallest length that can be measured using a standard 15-cm scale?
Answer:
The smallest length measurable is 1 millimetre (mm).
14. Why is it important to place the scale correctly while measuring?
Answer:
Placing the scale incorrectly can result in inaccurate readings. It should align along the object’s length.
15. Why should the eye be positioned directly above the scale while measuring?
Answer:
To avoid parallax error, which occurs when the scale is viewed at an angle, leading to incorrect readings.
16. Match the following lengths with appropriate units:
| Length | Unit |
|---|---|
| Distance between cities | Kilometre (km) |
| Thickness of a coin | Millimetre (mm) |
| Length of a pencil | Centimetre (cm) |
| Height of a room | Metre (m) |
17. Define periodic motion with examples.
Answer:
Periodic motion is motion that repeats itself after a fixed time interval. Examples:
- The swinging of a pendulum.
- The rotation of the Earth.
18. Why are some measuring devices made of flexible materials?
Answer:
Flexible materials allow measurement of irregular or curved objects, such as body measurements or round surfaces.
19. How would you measure the height of a tree?
Answer:
Use a long measuring tape or a shadow-based indirect method. Measure the shadow length of the tree and compare it with the shadow length of a known height.
20. What happens if we use non-standard units like handspan?
Answer:
Measurements would vary from person to person, leading to inconsistency and confusion.
21. How do we classify motion observed in a children’s park?
| Object | Type of Motion | Justification |
|---|---|---|
| Slide | Linear | Straight motion along the slide. |
| Merry-go-round | Circular | Circular motion along its path. |
| Swing | Oscillatory | Back-and-forth motion. |
22. Convert the following distances to centimetres:
- 3 m
- 0.5 km
Answer:
- 3 m=3×100=300 cm3 \, \text{m} = 3 \times 100 = 300 \, \text{cm}
- 0.5 km=0.5×1000×100=50,000 cm0.5 \, \text{km} = 0.5 \times 1000 \times 100 = 50,000 \, \text{cm}
23. What do kilometre stones with increasing numbers indicate?
Answer:
They indicate increasing distance from the reference point.
24. What types of motion are periodic?
Answer:
- Circular motion (e.g., a spinning wheel).
- Oscillatory motion (e.g., a pendulum).
25. How do you find the thickness of a single page of a book?
Answer:
Measure the thickness of a stack of 100 pages. Divide this value by 100 to find the thickness of a single page.
26. Why do different people have different handspan measurements?
Answer:
Handspan size varies due to differences in hand size.
27. What are standard units of length in the SI system?
Answer:
Kilometre (km), metre (m), centimetre (cm), millimetre (mm).
28. How does a magnetic compass help sailors?
Answer:
It helps sailors find direction by pointing towards the Earth’s magnetic north and south.
29. What is a periodic motion, and how does it differ from linear motion?
Answer:
Periodic motion repeats at regular intervals (e.g., a pendulum). Linear motion is a straight-line motion (e.g., a moving car).
30. Why are flexible tapes better for measuring curved surfaces?
Answer:
Flexible tapes can easily adapt to the shape of the surface, providing accurate measurements.
No Responses