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# Conceptual Physics

### Introduction to Physics & Chapter 4

Term | Definition |
---|---|

Units | A quantity that is ‘standard’ (known and used by many) for a particular measurement. |

Fundamental Units | They can not be expressed in term of other units. |

Prefixes | They are simply a number, specifically they are “powers of ten” and are expressed as letter symbols. |

Error | It refers to the difference between a measured value and the true value. |

% Error | |True value – Measured value| x 100 Accepted value (true value) |

Accuracy | It shows how close the answer is to the true value (accepted value). |

Uncertainty | It shows how limited your measuring device is. |

% Uncertainty | Uncertainty x 100 Measurement |

Precision | It shows how finite, or close, the measurement is. |

Significant Figures | They are the numbers in any measurement that we know with certainty, plus one digit that is uncertain. |

Scientific Notation | a method for expressing a given quantity as a number having significant digits necessary for a specified degree of accuracy, multiplied by 10 to the appropriate power. |

Relative | An object is moving is if its position is relative to a fixed point that is changing. |

Speed | It is a measure of how fast something is moving in a certain amount of time. |

Instantaneous Speed | The speed at any instant. |

Average Speed | The total distance covered divided by the time interval. |

Velocity | Speed in a given direction. |

Acceleration | The rate at which velocity changes. Fomula: change of velocity divided by the time interval. |

Free Fall | When there is no air resistance, and gravity is the only thing affecting a falling object. |

Elapsed Time | It is time that has passed since the beginning of any motion. |

Scalar Quantity | It has no direction associated with it. (Speed is one) |

Vector Quantity | It specifies both magnitude (size) and direction. (Acceleration is one) |