OLevel

## Physical Quantities | ## Base Unit | ## Symbol |

Length | meter | m |

Mass | kilogram | Kg |

Time | second | s |

Current | ampere | A |

Temperature | kelvin | K |

Amount of Substance | mole | mol |

Light Intensity | candela | cd |

## Value | ## Prefix | ## Symbol |

10^{-1} | deci | d |

10^{-2} | centi | c |

10^{-3} | mili | m |

10^{-4} | micro | µ |

10^{-5} | neno | n |

10^{3} | kilo | K |

10^{6} | mega | M |

10^{9} | giga | G |

A ruler can measure small distances

When measuring larger distances (of a few meters) a tape measure is more appropriate or, when measuring even larger distances, a trundle wheel. Users walk to the distance to be measured with trundle wheel and at the end it gives us readings.

Trundle wheels can be used to measure large distances

Measuring cylinders can be used to determine the volume of a liquid or an irregular shaped solid

- Suppose you have to measure the thickness of a sheet of paper. The thing that you are trying to measure is so small that it would be very difficult to get an accurate answer
- If, however, you measure the thickness of 100 sheets of paper you can do so much more accurately. Dividing your answer by 100 will then give an accurate figure for the thickness of one sheet
- This process of taking a reading of a large number of values and then dividing by the number, is a good way of getting accurate values for small figures, including (for example) the time period of a pendulum – measure the time taken for 10 swings and then divide that time by 10

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