Class 6 Science Chapter 5 Measurement of Length and Motion Notes & Summary in English for CBSE students
CBSE Class 6 Science Chapter 5 Notes & Summary in English for “Measurement of Length and Motion” (based on NCERT textbook Curiosity ).
Chapter 5 – Measurement of Length and Motion Complete Notes
(Complete Notes + Concept-wise Explanation + Summary CBSE Class 6 Science – Curiosity Book)
CHAPTER NOTES & SUMMARY
Chapter 5 – Measurement of Length and Motion
1. Introduction
The chapter begins with Deepa’s real-life experience of buying cloth and getting her dress stitched. This leads to discussions about how people measure length, why different methods give different results, and why standard units are necessary.
2. How Do We Measure?
2.1 Non-standard Units (Body Parts)
Earlier, people commonly used body parts to measure length:
- Handspan (balisht)
- Arm length
- Foot length
- Strides
- Finger width (angula)
Problems with body-part measurements:
They vary from person to person.
Example: Students measure the table using their handspan, and everyone gets different results.
Key Idea
A measurement needs:
- A number
- A unit
But the unit must be the same and standard for everyone.
3. Need for Standard Units
Because non-standard units differ, people across the world agreed to use SI Units (International System of Units).
SI Unit of Length: metre (m)
Other units:
- 1 km = 1000 m
- 1 m = 100 cm
- 1 cm = 10 mm
Older units still used sometimes:
- Inch
- Foot
4. Scales and Correct Way of Measuring
4.1 Choosing the Right Scale
- Small objects → 15-cm scale
- Big objects → metre scale or measuring tape
- Curved lengths → thread or flexible tape
4.2 Correct Use of a Scale
- Place scale in contact with the object.
- Keep eye directly above the marking (to avoid parallax error).
- If scale’s zero is broken:
- Start from another mark (e.g., 1 cm),
- Subtract the starting reading from ending reading.
For Visually Challenged Students
They use scales with raised markings felt by touch.
5. Measuring Curved Lines
A curved line cannot be measured with a straight scale.
Use:
- A thread, mark start to end, then straighten and measure, or
- A flexible measuring tape
6. Describing Position (Reference Point)
To know how far something is, you need a reference point.
Example:
Kilometre stones read “Delhi 70 km” → Delhi is the reference point.
Positions change if the object moves with respect to the reference point.
7. Motion and Rest
7.1 When is an object in motion?
An object is in motion if its position changes with respect to a reference point over time.
Example:
Passengers inside a bus appear at rest when bus is reference point.
Passengers appear in motion when buildings outside are the reference point.
7.2 When is an object at rest?
If its position does not change with respect to the reference point.
8. Types of Motion
8.1 Linear Motion
Object moves in a straight line.
Examples:
- Falling eraser
- March-past
- Pushed box
8.2 Circular Motion
Object moves along a circular path.
Examples:
- Merry-go-round
- Whirling a stone tied to a string
8.3 Oscillatory Motion
Object moves to and fro about a fixed position.
Examples:
- Swing
- Pendulum
- Vibrating metal strip
8.4 Periodic Motion
Motion that repeats after equal intervals of time.
Examples:
- Circular motion
- Oscillatory motion
Summary of Key Points – Measurement of Length and Motion
- SI unit of length is metre (m).
- 1 km = 1000 m, 1 m = 100 cm, 1 cm = 10 mm.
- A measurement = number + unit.
- Use correct placement of scale and correct eye position.
- A reference point is needed to describe position.
- Change of position with time → motion.
- Linear, circular, oscillatory, and periodic are the main types of motion.
Concept-Wise Detailed Explanation – Measurement of Length and Motion
A. Non-Standard vs Standard Units
Non-standard units differ, so measurements vary.
Standard units allow uniform, universal measurement.
B. Use of Metre Scale & Millimetre
A 1-cm section has 10 mm divisions → smallest measurable unit on that scale is 1 mm.
C. Parallax Error
If you look from the side, the reading looks different.
Always keep eye vertical to the reading point.
D. Curved Length Measurement
Direct scale won’t work.
Thread method gives accurate curved length.
E. Reference Point
Essential for comparing distances.
Without a reference, distance statements are meaningless.
F. Motion & Frame of Reference
Motion depends on where (or who) observes it from.
This is called frame of reference.
G. Types of Motion in Real Life
- Linear: Train moving on a straight track
- Circular: Hands of a clock
- Oscillatory: Guitar strings
H. Periodic Motion Meaning
Any movement that repeats at equal time intervals.
Chapter Short Summary – Measurement of Length and Motion
- Early measurements used body parts (handspan, arm length).
- Need for standard units led to SI units; metre is SI unit of length.
- Correct measuring methods prevent errors.
- Curved lengths need thread or flexible tape.
- Distance is meaningful only with a reference point.
- Motion = change of position w.r.t. time.
- 3 types of motion: linear, circular, oscillatory.
- Circular and oscillatory motions are periodic.