physics unit and measurement

Unit and measurement pratice question's and notes

Units and Measurement Practice Questions

  1. What are the fundamental units in the SI system?

    • The fundamental units in the SI system are:

      • Meter (m) for length

      • Kilogram (kg) for mass

      • Second (s) for time

      • Ampere (A) for electric current

      • Kelvin (K) for thermodynamic temperature

      • Mole (mol) for amount of substance

      • Candela (cd) for luminous intensity

  2. Convert 15 kilometers to meters.

    15 km=15×1000 m=15000 m15 \text{ km} = 15 \times 1000 \text{ m} = 15000 \text{ m}

  3. What is the difference between precision and accuracy?

    • Precision refers to the degree of reproducibility or agreement between repeated measurements. High precision means the measurements are very close to each other, but not necessarily close to the true value.

    • Accuracy refers to how close a measurement is to the true or accepted value. High accuracy means the measurement is close to the true value.

  4. A rectangular garden has a length of 10.5 meters and a width of 6.8 meters. Calculate its area with the correct number of significant figures.

    Area=Length×Width=10.5 m×6.8 m=71.4 m2Area = Length \times Width = 10.5 \text{ m} \times 6.8 \text{ m} = 71.4 \text{ m}^2

    Since 6.8 m has two significant figures, the area should be rounded to two significant figures: 71 m271 \text{ m}^2

  5. Convert 25°C to Kelvin.

    K=0˘0B0C+273.15K = \text{\u00B0C} + 273.15

    K=25+273.15=298.15 KK = 25 + 273.15 = 298.15 \text{ K}

  6. What is a light-year, and what is its value in meters?

    • A light-year is the distance that light travels in one year.

    • 1 light-year≈9.461×1015 meters1 \text{ light-year} \approx 9.461 \times 10^{15} \text{ meters}

  7. If the speed of an object is 20 m/s20 \text{ m/s}, what is its speed in km/h?

    20ms=20×3600 s1 h×1 km1000 m=72kmh20 \frac{\text{m}}{\text{s}} = 20 \times \frac{3600 \text{ s}}{1 \text{ h}} \times \frac{1 \text{ km}}{1000 \text{ m}} = 72 \frac{\text{km}}{\text{h}}

  8. Define systematic and random errors. Provide an example of each.

    • Systematic Errors:

      • Consistent and repeatable errors that affect all measurements in the same way.

      • Example: A miscalibrated instrument.

    • Random Errors:

      • Unpredictable errors that vary in magnitude and direction with each measurement.

      • Example: Fluctuations in environmental conditions.