๐ Class 7 Science Curiosity – Chapter 8 Notes
⏱️ Measurement of Time and Motion | Amresh Academy
๐ Introduction
๐ฐ️ 1. Measurement of Time
๐บ Ancient Timekeeping Devices
- ๐ Sundial → Uses shadow of sunlight
- ๐ง Water Clock → Measures time by water flow
- ⏳ Hourglass → Uses sand flow
- ๐ฏ️ Candle Clock → Based on burning rate
๐ Interesting Fact:
⚙️ Evolution of Clocks
- ⏱️ Mechanical Clocks (14th century) → gears & springs
- ๐ฐ️ Pendulum Clocks (17th century) → by Christiaan Huygens
- ⌚ Modern Clocks → Quartz & Atomic clocks
๐ 2. Simple Pendulum
๐ Definition:
๐ A small metal ball (bob) tied to a string
๐ Oscillation:
๐ One complete to-and-fro motion
⏳ Time Period:
๐ Time taken for one oscillation
๐ง Key Points:
- Depends on length of pendulum
- Does NOT depend on mass
๐งช Activity:
๐ Time for 10 oscillations ÷ 10 = Time period
๐ 3. SI Unit of Time
๐ Second (s) is SI unit
๐ Conversions:
- 60 seconds = 1 minute
- 60 minutes = 1 hour
๐ Rules:
- Use lowercase (s, min, h)
- Leave space (e.g., 5 s)
- No full stop
๐ 4. Speed
๐ Definition:
๐ Distance covered in unit time
๐ Formula:
๐ Units:
- SI unit → m/s
- Common → km/h
๐ Other Formulas:
- Distance = Speed × Time
- Time = Distance ÷ Speed
⚡ Average Speed:
๐ Total distance ÷ Total time
๐ 5. Uniform and Non-Uniform Motion
๐ Linear Motion:
๐ Motion in a straight line
✔️ Uniform Motion:
- Same speed
- Equal distances in equal time
❌ Non-Uniform Motion:
- Speed changes
- Unequal distances
๐ Examples:
- Train at constant speed → Uniform
- Car in traffic → Non-uniform
๐ Final Summary
๐ Key Concepts:
- Ancient to modern clocks ๐ฐ️
- Pendulum motion ๐
- Speed calculation ๐
- Types of motion ๐
✨ Perfect for revision + exams + concept clarity ๐
