Doubt Destroyer: Units, Dimensions, and Least Count- class 8

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Doubt Destroyer: Units, Dimensions, and Least Count

🔍 Doubt Destroyer: Units, Dimensions, and Least Count

1️⃣ Understanding Units

  • Physical Quantity: Anything that can be measured (e.g. length, time).
  • Unit: A standard quantity used to express a physical quantity.
  • Types of Units:
    • Fundamental Units: Cannot be derived from other units (e.g. metre, kilogram, second).
    • Derived Units: Formed by combining fundamental units (e.g. m/s, N, J).
  • SI System: International System of Units — the standard for scientific measurement.

2️⃣ Dimensions Demystified

Dimensions express a physical quantity in terms of base quantities like mass (M), length (L), and time (T).

  • Example: Speed has dimensions of [L T-1]
  • Force: [M L T-2]
🧠 Why are dimensions important?
– To check if equations are dimensionally correct
– To derive formulas
– To convert units

3️⃣ Least Count Explained

Least Count is the smallest value that can be measured by an instrument.

  • Ruler: Least count = 1 mm or 0.1 cm
  • Vernier Calliper: Least count = 0.01 cm
  • Screw Gauge: Least count = 0.001 cm
Concept Tip: Smaller least count = Higher accuracy.

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