There are many bumping and mass elements in mechanics model. In order to easily work out the transfer function of mechanics system model

we can take these elements as elastic elements in imaginary domain. A new coneept called imaginary elastic rigidity is introdnced. It is similar to imaginary resistance in electric metwork systems. Different kinds of elements can be seen as elastic elements in parallel or in series and can be handled with the same concept while in accordance with relevent physical laws. This method eliminates the necessity of differential equations to get transfer functions. We can conveniently and directly obtain the block diagrams of systems. This method is useful and simple. 