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# Physics Definitions

### Module 3 Work and Energy

Question | Answer |
---|---|

Work done by a force | The product of the force and the distance moved in the direction of the force |

The joule | This is a unit of energy 1J is the work done when a force of 1N moves it's point of application 1m in the direction for the force |

Conservation of energy | States that energy cannot be created or destroyed, just converted from one form to another or transferred from one place to another |

Power | Rate of work done. Measured in Watts |

The watt | A unit of power. 1 Watt is 1J of energy transferred per second |

Efficiency | The ratio of useful output energy to total input energy |

Tensile force | Usually two equal and opposite force acting on a wire in order to stretch it |

Compressive force | Two or more forces that have the effect on reducing the volume of the object on which they are acting or reducing the length |

Extension(x) | the change in length of an object when subjected to tension |

Elastic Limit | The point at which elastic deformation becomes plastic deformation |

Limit of proportionality | The point at which at which an object no longer obeys Hooke's law |

Force constant(k) | Force per unit extension or compression |

Hooke's law | The extensions of an elastic body is proportional to the force that causes it to up the limit of proportionality |

Elastic potential energy | The energy stored in a stretched or compressed object (E.G. a spring) |

Stress | The force per cross-sectional area. |

Strain | The extension per unit length |

Young's modulus(y) | The ratio between stress and strain |

Ultimate tensile strength | the maximum tensile force that can be applied to an object before it breaks |

Breaking stress | The maximum stress that can be applied to an object before it breaks |

Elastic deformation | The object will return to it's original shape when the deforming force has been removed |

Plastic deformation | The object will not return to it's original shape when the deforming force is removed, it becomes permanently deformed |

Ductile material | Materials that have a large plastic region and can therefore be drawn into a wire (E.G. copper) |

Brittle material | A material that distorts very little even when subject to a large stress and does not exhibit any plastic deformation (E.G. concrete) |

A polymeric material | A material made of many smaller molecules bonded together, often making a tangle knot of chains (E.G. rubber) these materials often exhibit very large strains (E.G. 300%) |