Let be a Cartesian basis fixed in the rotating frame. A vector then satisfies
because a derivative of a body-fixed basis vector is . Applying this transport formula twice to gives, for constant ,
The second and third terms correspond to Coriolis acceleration and centrifugal acceleration in the rotating description.
For the bead, use cylindrical unit vectors with upward and
Projection of along the wire tangent eliminates the smooth-wire normal force and gives
In a frame with unit angular velocity, transforming the acceleration introduces the Coriolis acceleration and centrifugal acceleration. Radiation reduces the attraction of by the factor , so
With the effective potential
its Cartesian components are exactly
This is the photogravitational restricted three-body problem.
The term is the Coriolis acceleration, and is the centrifugal acceleration. With , the Cartesian components are
At a Lagrange point, the test particle is stationary in the rotating reference frame, so . On the axis, makes automatically. The singularities at the two masses split the axis into three intervals, and the balance between gravity and centrifugal acceleration gives one root of in each interval. These are the three Collinear Lagrange points .
For an off-axis equilibrium, . Put . Then
while
Hence and therefore . The two intersections of unit circles centered at and form equilateral triangles with the binary, giving the Triangular Lagrange points
Together with the three collinear points, these are the five equilibria of the circular restricted three-body problem.
Rotating-frame derivative formula Created 2026-09-29 Updated 2026-10-05
If a frame rotates with angular velocity relative to an inertial frame, the derivatives of any vector satisfy
Applying this formula twice to a position gives the Coriolis acceleration, Euler acceleration, and centrifugal acceleration terms.
In an Earth-fixed rotating reference frame, the horizontal displacement of a freely falling body receives contributions from Coriolis acceleration and centrifugal acceleration. A short-fall approximation substitutes the unperturbed downward velocity into the Coriolis term and the Earth's surface position into the centrifugal term. If gravitational acceleration excludes centrifugal acceleration, both contributions must be included explicitly.