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Physical quantities are either scalars or vectors.
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Scalars don’t have a direction.
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Vectors have a direction.
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SI units
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SI base units include:
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m
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kg
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s
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A
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K
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Derived units are based on base units, for example:
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m/s
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m/s2
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N (which really means kgm/s2)
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Prefixes can be used if a unit is too big or too small for a purpose.
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mega (M) means 1,000,000
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kilo (k) means 1,000
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deci (d) means 1 / 10
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centi (c) means 1 / 100
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milli (m) means 1 / 1,000
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micro (µ) means1 / 1,000,000
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Length measuring instruments
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Ruler or measuring tape has an accuracy of ±1mm.
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Vernier calipers has an accuracy of ±0.1mm.
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Micrometer screwguage has an accuracy of ±0.01mm.
- To measure length using vernier calipers or micrometer screwguage:
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Length = Main scale reading + Minor scale reading x Accuracy
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Time measuring instruments
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Stopwatch has an accuracy of ±0.01s
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Ticker-tape timer has an accuracy of ± (1 / 50) of a second or ± (1 / 60) of a second.
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Pendulum clock
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Pendulum
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Oscillation is a vibration.
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Time-period is the time taken for one oscillation.
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Amplitude is the maximum displacement from central position.
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A pendulum of a particular length has a constant time-period. It is not affected by amplitude.
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