# Physical Quantities and Units - Unit 1

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- Created by: Joe McFarlane
- Created on: 18-02-13 18:02

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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

- independent quantities in terms of which other quantities can be defined
- 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

- Quantities that are obtained by multiplying or dividing base quantities
- 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

- Are used to form decimal multiples and submultiples of SI units
- 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.

- 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
- 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

- Precision is how consistently a measurement is recorded.

- Base Quantities

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