Re-entry,
in Matthew's equation, 9.81 m/sē just means g, the gravity acceleration,
considered as a constant value (here it does NOT mean the load factor, variable).
The equation is derived from expressing the centripetal acceleration in 2 different ways:
1) a = vω
centripetal acceleration = true airspeed * angular speed (in rad/s)
For rate one, angular speed is : 2π /120s
2) a/g = tan(γ)
centripetal acceleration / gravity acceleration = tangent ( bank angle )