The motion of a particle described by the Langevin equation with constant diffusion coefficient,
time dependent linear force ( ##IMG##
[http://ej.iop.org/images/0143-0807/38/6/065104/ejpaa8d54ieqn1.gif] {$\omega (1+\alpha \cos ({\omega
}_{1}t))x$} ) and periodic load force ( ##IMG##
[http://ej.iop.org/images/0143-0807/38/6/065104/ejpaa8d54ieqn2.gif] {${A}_{0}\cos ({\rm{\Omega
}}t)$} ) is investigated. Analytical solutions for the probability density function (PDF) and n
-moment are obtained and analysed. For ##IMG##
[http://ej.iop.org/images/0143-0807/38/6/065104/ejpaa8d54ieqn3.gif] {${\omega }_{1}\gg \alpha \omega
$} the influence of the periodic term ##IMG##
[http://ej.iop.org/images/0143-0807/38/6/065104/ejpaa8d54ieqn4.gif] {$\alpha \cos ({\omega }_{1}t)$}
is negligible to the PDF and n -moment for any time; this result shows that the statistical averages
such as n -moments a…