Module 2- Foundations of physics

• Physical quantities —> A physical property of a phenomenon, body, or substance, that can be quantified by measurement.
• Unit of measurement —> A definite magnitude of a physical quantity, that is used as a standard for measurement of the same physical quantity.
• Length (SI) —> metres (m)
• Mass (SI)—> kilograms (Kg)
• Time (SI) —> seconds (s)
• Electrical current (SI) —> Amperes (A)
• Temperature (SI) —> Kelvin (K)
• Amount of substance (SI) —> moles (mol)
• 0 degrees Celsius = 273K. A change in 1 degree Celsius = change in 1K
• peta —> P = 10^15
• tera —> T = 10^12
• giga —> G = 10^9
• mega —> M = 10^6
• kilo —> k = 10^3
• deci —> d = 10^-1
• centi —> c = 10^-2
• Milli —> m = 10^-3
• micro —> 10^-6
• nano —> n = 10^-9
• pico —> p = 10^-12
• femto —> f = 10^-15
• Homogeneity —> An equation must have the same units on either side if it is to be correct
• Checking for homogeneity:

  • Take an equation and convert into base units
  • Prove both sides are equal by cancelling the units down
  • E.g: I=nAve
• 1m^2 = 10000cm^2 = 1000000mm^2
• Accurate —> A measurement that is judged to be close to the true/ acceptable value
• Precise —> closeness of agreement between measured values obtained by repeated measurements
• Repeatable —> A measurement is repeatable when repetition under same conditions gives similar results
• Reproducible —> A measurement is reproducible when similar results are produced by different groups/ equipment
• Random error —> Error in measurement due to small uncontrollable effects
• Systematic error —> Error due to the measured value differing from the true value by the same amount each time
• Absolute uncertainty —> The actual amount by which the quantity is uncertain
• Percentage uncertainty —> fractional uncertainty expressed as a percent
• Avoid parallax error by:

  • Placing object as near to the scale of measuring scale as possible
  • Place your eye directly above the measuring scale
• Error bars —> a line through a point on a graph, parallel to the one of The axes, which represent the uncertainty of the point
• Uncertainty —> measure of the limit of how far your measured value could be from the true value
• Percentage uncertainty = absolute uncertainty/ measured mean value x100
• Calibrated —> (of an instrument) marked with a scale of readings
• Recording measurements:

  • When using a digital measuring device -> record all digits shown (for a digital timer don’t record to more than 2dp)
  • When using a non-digital device —> record all the figures that are known and where appropriate an additional estimate figure may be allowed
• Mean values —> when calculating mean values of measurements, it is acceptable to increase the number of significant figures by 1
• Table headings :

  • It is expected that all table column (or row) headings will consist of a quantity and unit
  • The quantity may be represented by a symbol in italics, heile units are upright