Mechanical power flow into a discrete system is formulated as power dissipation in the system using driving point advantages. Firstly, the complex-valued power flow into a system is defined, and it is shown that the real part (or active power) corresponds to the power dissipation, and the imaginary part (or reactive power) contains the Lagrangian energy. To represent the power dissipation in the system, all the power flows into the system must be counted. Otherwise, the value of power flow may become negative, and its physical interpretation may be troublesome. One of the main advantages of the formulated power flow is that to estimate the power dissipation in the system, only the power flows into the system are necessary. In other words, only the driving point power flows into the system are needed, and no information inside the system is required. Next, to estimate interfacial force/moment for the power flow into a sub-system, the two alternative indirect methods are presented. It is shown that these are exact methods utilizing the responses and the frequency response functions at the driving points only. This is another remarkable characteristic of the driving point. A 7 degree-of-freedom system is employed as an example case, and the presented formulations are confirmed computationally.

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