  This paper considers the analogy between the force exerted on cold atoms when
they interact with a highly twisted tightly focused laser beam and the forces
exerted on a charged dielectric particle inside a uniform electric field when
we perform the Millikan's experiment. In the later case the particle
experiences its weight, a force due to the electric field which is arranged in
the opposite direction of the weight, and a drag force due to the air
proportional and opposite to the velocity of the particle. The force due to the
electric field is "quantised" since the charge of the particle is always an
integer multiple of the electron charge. In the case of the cold atoms the
total force is made up by three terms. The second term is quantised since it is
proportional to the beam helicity which is an integer number. The sign of this
term is opposite to the first. The third term is a damping force force
proportional and opposite to the velocity of the atom. We present numerical
calculations with parameters taken from experimental data which show an
impressive analogy between the involved forces.
