Chapter 1:Physical Quantities and Measurement Techniques

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Core

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1. Using Rulers and Measuring Cylinders

• Ruler (for length):

  • Used to measure lengths of objects in cm or mm.

  • Place the object close to the ruler’s zero mark to reduce parallax error.

  • Ensure your eyes are level with the measurement mark to avoid reading errors.

• Measuring Cylinder (for volume):

  • Used to measure the volume of liquids.

  • Read the bottom of the meniscus (the curved surface of the liquid) at eye level.

  • Units are typically in millilitres (ml) or cubic centimetres (cm³).

• Irregular Objects:

  • Use the displacement method:

    1. Fill the measuring cylinder with water and record the initial volume.

    2. Submerge the object completely.

    3. Record the final volume.

    4. Volume of the object = Final volume − Initial volume.

2. Measuring Time Intervals

• Analogue clocks and stopwatches:

  • Have hands or dials.

  • Useful for longer time intervals.

  • Can be harder to read precisely.

• Digital stopwatches/timers:

  • Display time in decimal format (e.g., 0.01 s).

  • Provide more accurate and easier-to-read measurements.

  • Used for short intervals like reaction times or experiment timing.

3. Determining Average Values

• Average (Mean) = Total quantity ÷ Number of readings

• Small distances:

  • For small lengths (e.g., width of a wire), measure multiple wires side by side and divide total length by number of wires.

  • Short time intervals:

  • For very short durations (e.g., one swing of a pendulum), measure the time for multiple oscillations (e.g., 10 or 20 swings) and divide by the number of swings:

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• This method reduces timing errors and increases accuracy.

 

 

Extended 

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Scalar and Vector Quantities

• Scalar quantity: Has magnitude (size) only

• Vector quantity: Has both magnitude and direction.

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