# Velocity

Velocity is a vector quantity that specifies the time rate of change of displacement with respect to a reference frame. If the reference frame is not inertial, the velocity is often designated "relative velocity".

1 mph | = | 1.609 km/h | 1 ms^{-1} | = | 3.2808399 fts^{-1} | |

1 in s^{-1} | = | 0.0254 ms^{-1} | 1 ft s^{-1} | = | 0.3048 ms^{-1} | |

1 km h^{-1} | = | 0.2778 ms^{-1} | 1 ft min^{-1} | = | 0.00508 ms^{-1} | |

1 knot | = | 0.5144 ms^{-1} |

1km h^{-1} = 1 km/h = 1000 m/h = 1000/3600 m/s = 0.2778m/s

Note: if using this type of conversion within a calculation then best to use 1000/3600 in the calculation rather than the value round to 4 decimal points.

Snail | 0.013 ms^{-1} |

Fast walk | 1.79 ms^{-1} (4 mph) |

Stephenson′s Rocket | 13.4 ms^{-1} (30 mph) |

Steam train speed record | 56.3 ms^{-1} (126 mph) |

Fastest boat (Spirit of Australia 1978) | 141.95 ms^{-1} (317.6 mph) |

Land speed record (Thrust SSC 1997) | 341.0 ms^{-1} (763 mph) |

Concorde | 597 ms^{-1} (1336 mph) |

Fastest plane (SR71 BlackBird) | 980 ms^{-1} (2193 mph) |

Escape velocity at surface of the Moon | 2.38x10^{3} ms^{-1} |

Escape velocity at surface of the Earth | 1.12x10^{4} ms^{-1} |

Escape velocity at surface of the Sun | 6.18x10^{5} ms^{-1} |

Speed of light in vacuo | 2.998x10^{8} ms^{-1} |

### Acknowledgement

We would like to thank Peter W Kruhøffer for pointing out the error in our conversion table from km h^{-1} to ms^{-1}

**See also: **Acceleration, Angular Velocity, Displacement, Escape Velocity, Hypervelocity, Instantaneous Speed, Kilometres Per Hour, Length, Miles Per Hour, SI Units, Straight-Line Speed.

**Subjects: ** Classical Mechanics