# Length

Written by Jerry Ratzlaff on . Posted in Classical Mechanics

Length, abbreviated as l, 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.

## Length formula

 $$\large{ \Delta l = l_f - l_i }$$

### Where:

 Units English Metric $$\large{ l }$$ = length $$\large{ft}$$ $$\large{m}$$ $$\large{ \Delta l }$$ = length differential $$\large{ft}$$ $$\large{m}$$ $$\large{ l_f }$$ = final length $$\large{ft}$$ $$\large{m}$$ $$\large{ l_i }$$ = initial length $$\large{ft}$$ $$\large{m}$$

## Related length formulas

 $$\large{ l = \frac {\pi\; r\;\theta}{180} }$$ (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

$$\large{ \Delta l }$$ = length differential

$$\large{ \theta }$$  (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

$$\large{ l_f }$$ = 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

Tags: Equations for Length