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# Mechanics Def'ns

### MechanicsDefinitions

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

Physical Quantity | A quantity that can be measured, or calculated, and expressed in numbers |

Scalar Quantity | A quantity with magnitude only, not direction |

Distance | A measure of how far one point is from another |

Displacement | An object's overall change in position |

Time | Used to measure the duration of an event or the interval between events |

Speed | Rate of change of distance with respect to time |

Vector Quantity | A quantity with both magnitude and direction |

Velocity | Rate of change of displacement with respect to time |

Acceleration | Rate of change of velocity with respect to time |

Mass | A measure of the amount of matter in a body |

Momentum | The product of mass and velocity |

Force | That which causes acceleration |

Acceleration due to gravity | The acceleration experienced by a body in free fall within the gravitational field of a massive body |

Weight | A force equal to the product of mass and acceleration due to gravity |

Centre of gravity | The point at which the whole weight of a body appears to act |

Friction | A force that opposes the motion of a body |

Moment of a Force | The force multiplied by the perpendicular distance to the fulcrum |

Lever | A rigid body that is free to rotate about a fixed axis |

Couple | A pair of equal and opposite forces whose lines of action do not coincide |

Torque of a Couple | Product of the magnitude of one of the forces and the distance between the two forces |

Density | Mass per unit volume |

Pressure | Force per unit area |

Buoyancy | Upward force on a body that is wholly or partly immersed in a fluid |

Work | Product of force and displacement |

Energy | Ability to do work |

Kinetic Energy | Energy a body has due to its motion |

Potential Energy | Energy a body has due to its position |

Power | Rate at which work is done |

Radian | A measure of angle found by dividing arc length by radius |

Angular Velocity | Rate of change of angle with respect to time |

Linear Velocity | Rate of change of displacement with respect to time in a direction perpendicular to the radius at that point |

Periodic Time | Time taken for one complete revolution, cycle or oscillation |

Centripetal Acceleration | Acceleration of an object travelling in uniform circular motion, directed towards the centre of the circle |

Centripetal Force | Force required to keep up uniform circular motion, directed towards the centre of the circle |

Elastic Constant | Constant of proportionality between force applied and the resulting displacement of spring/elastic string |

Elasticity | Ability of a body to resist a distorting influence or stress and to return to its original shape and size when the stress is removed |

Simple Harmonic Motion | When the acceleration of a body towards a particular point is proportional to displacement away from that point |

Amplitude | Maximum distance an object moves away from its equilibrium position |

Frequency | Number of revolutions, cycles or oscillations an object completes per unit time |

Period of SHM | Time taken for one complete revolution, cycle or oscillation |