Physical Quantities and Units - Unit 1

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  • Physical Quantities and Units - Unit 1
    • Base Quantities
      • independent quantities in terms of which other quantities can be defined
        • Temperature, kelvin, K
        • Time, seconds, s
        • Mass, kilogram, k
        • Length, metres, m
        • Current, amperes, A
    • Derived Quantities
      • Quantities that are obtained by multiplying or dividing base quantities
        • Velocity, v=s/t, ms^-1
        • Energy (potential, e.g.), mgh, kgm^2s^-2
        • Density, p=m/v, kgm^-3
        • Volume, hxlxw, m^3
        • Acceleration,a= (u-v)/t, ms^-2
        • Frequency= 1/T, s^-1
    • Prefixes
      • Are used to form decimal multiples and submultiples of SI units
        • kilo, k, x10^3
        • Mega, M, x10^6
        • Giga, G, x10^9
        • Tera, T, x10^12
        • deci, d, x10^-1
        • centi, c, x10^-2
        • mili, m, x10^-3
        • micro, µ, x10^-6
        • nano, n, x10^-9
        • pico, p, x10^-12
    • Estimations
      • make reasonable estimates of physical quantities included within the syllabus 
    • Errors/Uncertainties
      • Systematic errors are errors caused by the apparatus or the method used. It results in a complete shift of the results away from the true value
        • To spot systematic errors, for a results graph where the gradient is constant, the y-intercept will not be 0. Can be corrected by correcting apparatus accordingly.
      • Random errors are errors caused by the experimenter, causing a scatter of results around the true value.
        • Can be corrected by taking many readings, discarding anomolies and taking an avg.
      • The uncertainty of a scale is its smallest reading.
      • Relative Error: Error/Actual Value
      • Percentage error: Error/Actual Value) x100
      • Addition/Subtraction -> Add up errors. Multiplication/Division -> Add up % errors.
    • Precision/Accuracy
      • Precision is how consistently a measurement is recorded.
        • Precision refers to the degree of agreement of the results
      • Precision refers to the degree of agreement of the results
      • Accuracy is the degree of scatter about the true value
      • Accuracy refers to how close the results are to the true value
        • Accuracy is the degree of scatter about the true value

Comments

Mrs Jones

This is a great way to display all the confusing stuff talked about units and measurements.  Nail this and your practical marks and use of units in calculations will improve.  Do you know your prefixes?  Test yourself using a print off and keep it at the front of your file for easy reference :-)

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