# Length

Length (also called distance) is the dimension from one point to another point or the dimension from one end to the other end of an object.

## Formulas that use length

\(\large{ \Delta l = l_f - l_i }\) | |

\(\large{ l = \frac {\pi\; r\;\theta}{180} }\) | (angular deflection) |

\(\large{ l = \frac { 2 \; h_l \; d_p \; g } { f_d \; v^2 } }\) | (Darcy-Weisbach equation) |

\(\large{ l = \frac { h_1 \;-\; h_2} { i} }\) | (hydraulic gradient) |

\(\large{ l = \frac{ \lambda }{ Kn } }\) | (Knudsen number) |

\(\large{ l = k_t \; \frac{\Delta T}{\dot {Q}_t} }\) | (linear thermal expansion coefficient) |

\(\large{ l = \frac {M}{F} }\) | (moment) |

\(\large{ l_s = \sqrt{ \frac{ 2 \; PE_s }{ k_s } } }\) | (spring potential energy) |

\(\large{ \Delta l = \epsilon \; l_i }\) | (strain) |

### Where:

\(\large{ l }\) = length

\(\large{ \theta }\) (Greek symbol theta) = angular deflection

\(\large{ f_d }\) = Darcy friction factor

\(\large{ F }\) = force

\(\large{ g }\) = gravitational acceleration

\(\large{ h_l }\) = head loss

\(\large{ \dot {Q}_t }\) = heat transfer rate

\(\large{ i }\) = hydraulic gradient

\(\large{ Kn }\) = Knudsen number

\(\large{ \Delta l }\) = length differential

\(\large{ l_f }\) = final length

\(\large{ l_i }\) = initial length

\(\large{ r }\) = minimum centerline bend radius for constant flexing

\(\large{ v }\) = mean flow velocity

\(\large{ \lambda }\) (Greek symbol lambda) = mean free path

\(\large{ M }\) = moment

\(\large{ \pi }\) = Pi

\(\large{ d_p }\) = inside diameter of pipe

\(\large{ h_1 }\) = pressure head at point 1

\(\large{ h_2 }\) = pressure head at point 2

\(\large{ k_s }\) = spring force constant

\(\large{ PE_s }\) = spring potential energy

\(\large{ \epsilon }\) (Greek symbol epsilon) = strain

\(\large{ \Delta T }\) = temperature differential

\(\large{ k_t }\) = thermal conductivity constant