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