Physics: SI Base and Derived Units
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Questions and Answers

Which SI base unit corresponds to the quantity 'mass'?

  • Ampere
  • Second
  • Kilogram (correct)
  • Meter

    • What is the derived unit for electric charge based on the SI base units?

  • Joule
  • Newton
  • Coulomb (correct)
  • Volt

    • What metric prefix denotes one thousand times a unit?

  • Milli
  • Kilo (correct)
  • Centi
  • Deci

    • Which of the following pairs correctly match the physical quantity with its base unit?

    <p>Temperature - Kelvin</p> Signup and view all the answers

    Which of the following base units is used to measure luminous intensity?

    <p>Candela</p> Signup and view all the answers

    What is the primary benefit of using the metric system over nonmetric systems?

    <p>It relies on sequential powers of 10 for measurement.</p> Signup and view all the answers

    Which of the following is correctly represented as a conversion factor?

    <p>100 meters/1 kilometer</p> Signup and view all the answers

    What are placeholder zeros used for in numbers that are 10 or greater?

    <p>To fill in decimal places left after movement.</p> Signup and view all the answers

    How is scientific notation commonly represented?

    <p>x × 10y</p> Signup and view all the answers

    Why might you switch from meters to kilometers when measuring distance?

    <p>To indicate a larger value conveniently.</p> Signup and view all the answers

    In scientific notation, how is the exponent determined when moving the decimal point to the right?

    <p>It is negative.</p> Signup and view all the answers

    If you convert 80 meters to kilometers, which conversion factor would you use?

    <p>1 km/1000 meters</p> Signup and view all the answers

    When converting 92,955,807 miles to kilometers using the conversion factor 1 mile = 1.6 km, what is the original distance in kilometers before scientific notation?

    <p>148,729,291.2 km</p> Signup and view all the answers

    What is the scientific notation representation of the number 0.0000045?

    <p>4.5 × 10^-6</p> Signup and view all the answers

    What does 'x' represent in scientific notation?

    <p>The value of the measurement without placeholder zeros</p> Signup and view all the answers

    What does accuracy in measurements indicate?

    <p>The nearness of measurements to the true value</p> Signup and view all the answers

    Which of the following exemplifies a nonmetric system?

    <p>Inches and feet</p> Signup and view all the answers

    How many times do you move the decimal point to convert 148,729,291.2 km into scientific notation?

    <p>8 times</p> Signup and view all the answers

    How is the weight of a person measured in pounds if they weigh 60 kg with the conversion factor 1 kg = 2.2 lbs?

    <p>132 lbs</p> Signup and view all the answers

    What primarily determines precision in measurement?

    <p>The variation in measured values from repeated attempts</p> Signup and view all the answers

    Which of these is NOT a characteristic of conversion factors?

    <p>They can only be used in metric measurements.</p> Signup and view all the answers

    What step is NOT part of the process for converting a number into scientific notation?

    <p>Calculating the square of the number.</p> Signup and view all the answers

    Which type of error cannot be completely eliminated in measurements?

    <p>Both random and systematic errors</p> Signup and view all the answers

    What is the absolute error defined as?

    <p>The difference between actual and measured value</p> Signup and view all the answers

    What is the value of y in the scientific notation of a number when the decimal is moved 6 places to the left?

    <p>-6</p> Signup and view all the answers

    What impact does eliminating systematic error have?

    <p>Improves accuracy but does not change precision</p> Signup and view all the answers

    Which statement about accuracy is incorrect?

    <p>Accuracy indicates the closeness of results to one another</p> Signup and view all the answers

    What does a higher variance indicate about measurements?

    <p>Less consistency among measurements</p> Signup and view all the answers

    In terms of accuracy, which of the following is true?

    <p>It reflects the closeness of measurements to both the actual value and each other</p> Signup and view all the answers

    What is the correct formula for calculating Relative Error?

    <p>Relative Error = Absolute Error / Measured Value</p> Signup and view all the answers

    If a fence measured 12.5 meters with an Absolute Error of ±0.05 m, what is the Percentage Error?

    <p>0.4%</p> Signup and view all the answers

    What is the first step in calculating Variance based on a data set?

    <p>Calculate the mean of the data set</p> Signup and view all the answers

    If the accepted distance from Candon City to Baguio City is 125 miles and the measurements are 151, 152, 148, and 149 miles, what is the average of these measurements?

    <p>150 miles</p> Signup and view all the answers

    What is the Absolute Error when the thermometer reads 38°C with a ±1° accuracy?

    <p>1°</p> Signup and view all the answers

    What is the correct expression for finding Variance?

    <p>Variance = (Sum of squared distances) / (Number of values)</p> Signup and view all the answers

    If the Relative Error for a measurement is 0.0263, what is the Absolute Error if the actual measurement is 38°C?

    <p>1°</p> Signup and view all the answers

    How is the Percentage Error derived from the Relative Error?

    <p>By dividing the Absolute Error by the Measured Value and multiplying by 100</p> Signup and view all the answers

    Study Notes

    SI Base Units

    • Seven base units form the foundation of the International System of Units (SI).
    • Five primary base units used are:
      • Length: Meter (M)
      • Mass: Kilogram (Kg)
      • Time: Second (S)
      • Electric Current: Ampere (A)
      • Temperature: Kelvin (K)
    • Two additional base units:
      • Amount of Substance: Mole (Mol)
      • Luminous Intensity: Candela (Cd)
    • Derived units are formed by mathematically combining base units.

    Metric Prefixes

    • The metric system utilizes prefixes to handle varying sizes, with each prefix representing a power of ten.
    • Common conversions:
      • 100 centimeters (cm) = 1 meter (m)
      • 1000 meters (m) = 1 kilometer (km)
    • The metric system simplifies large and small measurements using appropriate prefixes, avoiding the need for new units.
    • Other non-metric units, like inches and feet, have more complex relationships.

    Unit Conversion and Dimensional Analysis

    • Conversion factors express the relationship between different units and are equal to one (e.g., 1 foot/12 inches).
    • Conversion example: 80 meters can be converted to kilometers using the factor (1 km/1000 m).
    • This method is essential in dimensional analysis to maintain unit consistency in calculations.

    Scientific Notation

    • Used for representing very large or small numbers for convenience.
    • General format is x × 10^y, where x is a non-zero digit and y indicates decimal movement.
    • Example: 840,000,000,000,000 = 8.40 × 10^14; 0.0000045 = 4.5 × 10^(-6).

    Measurement Accuracy and Precision

    • Accuracy: Closeness of a measurement to the true value.
    • Precision: Consistency of repeated measurements, showing how close they are to each other.
    • Random Error: Caused by unpredictable variations (e.g., temperature fluctuations).
    • Systematic Error: Arises from systematic biases in measurement tools, which are harder to eliminate.

    Error Estimation

    • Absolute Error: Difference between actual and measured values, approximated when the actual value is unknown.
    • Relative Error: Absolute error divided by the actual measurement.
    • Percentage Error: Relative error expressed as a percentage.

    Variance Calculation

    • Variance measures how individual data points differ from the mean.
    • Calculation involves:
      • Subtracting the mean from each value.
      • Squaring the results.
      • Dividing the sum of squares by the number of measurements.

    Practical Examples

    • Example of converting Earth-Sun distance from miles to kilometers, finding a result in scientific notation.
    • Example of weight conversion from kilograms to pounds using conversion factors.
    • Example of calculating errors with a fence measurement and thermometer readings, including calculating absolute, relative, and percentage errors.

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    Description

    This quiz covers the concepts of SI base units and how derived units are formed through mathematical combinations of these units. Focused on length, mass, time, electric current, and temperature, the quiz will help solidify your understanding of these fundamental concepts in physics.

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