All questions of Measurement of Length and Motion for Class 6 Exam

The hands of a clock move in a circular path around the center of the clock face.

To avoid parallax error, the eye should be directly above the point of measurement.

Measurement ensures that we can communicate quantities effectively and consistently, which is crucial for tasks like buying fabric, cooking, or building structures.

A reference point is a fixed point used to describe the position of an object, providing a basis for comparison.

Understanding Periodic Motion
Periodic motion refers to any motion that repeats itself at regular intervals of time. It is characterized by a cycle, which is a complete sequence of motions that returns to the starting point.
Why Option B is Correct
- The Earth rotating on its axis is a classic example of periodic motion:
- Regular Interval: The Earth takes approximately 24 hours to complete one full rotation.
- Predictable Cycle: This rotation causes day and night, which occur in a predictable pattern.
- Repetitive Nature: Every day, the Earth returns to the same position relative to the sun, fulfilling the criteria of periodicity.
Other Options Explained
- Option A: A car stopping at a signal
- This motion is not periodic as it does not repeat at regular intervals. The timing of the stops depends on traffic signals, which can vary.
- Option C: A person walking randomly
- Random walking does not follow a set pattern or cycle, making it non-periodic. The path taken is unpredictable.
- Option D: A book lying on a table
- The book is stationary and does not exhibit any motion, periodic or otherwise.
Conclusion
In conclusion, among the given options, the Earth's rotation on its axis (Option B) is the only example of periodic motion due to its consistent and repeating nature over a defined time frame.

Explanation:

Oscillatory Motion:
When an object moves back and forth about a fixed position, it is known as oscillatory motion. This type of motion involves the object repeatedly moving between two points or positions.

Characteristics of Oscillatory Motion:
- The object moves to and fro around a central or equilibrium position.
- The motion is periodic, meaning it repeats at regular intervals.
- The object experiences acceleration towards the equilibrium position.

Examples of Oscillatory Motion:
- A swing moving back and forth.
- A pendulum swinging from side to side.
- A vibrating tuning fork.

Applications of Oscillatory Motion:
- Oscillatory motion is used in various devices such as clocks, metronomes, and tuning forks.
- It is also utilized in systems like springs and shock absorbers.
In conclusion, oscillatory motion involves the repeated movement of an object back and forth about a fixed position. This type of motion is characterized by its periodic nature and is commonly observed in everyday objects and devices.

Curved lines can be accurately measured using a thread and then measuring the thread with a measuring tape.

The metre is the standard unit of length in the SI system.

Traditional methods varied greatly because people's body parts differ in size, leading to inconsistencies in measurements.

Kilometres are used to measure long distances, such as the distance between cities.