# Load factor as a result of constant roll rate

The fuel pressure load equation for an aircraft in a constant roll maneuver has the term (as a result of the roll maneuver):

$\frac{\dot{\phi^2}}{2g}R^2$

where

$R$ - radius from center of fuselage
$g$ - gravitational constant
$\dot{\phi}$ - roll rate

my question is where does the "2" next to the gravitational constant come from?