Every day we experiment motion and shape change of continuum media, assembly of different space dimension structures, fluids, solids which exhibit numerous evolutions either particular or general: large deformations, incompressibility, cavitation, contact, surface tension, defects, dislocations,... Stretch and rotation are a common feature of these motions and phenomenons. We base a continuum mechanics predictive theory on stretch and rotation quantified by matrices. The powers which intervene in the principle of virtual power are investigated in this Chapter with the stretch velocity and the angular velocity. The actual power to change the shape is easy to experiment but it is a difficult and sophisticated task to quantify it. Based on experiments, it is defined as a linear function of the derivatives up to the order two of the stretch and angular velocities. Based also on experiments, the actual power to change the velocity is a linear function of the derivatives up to the order two of the stretch and angular velocities. The actual external power provided to the system depends also on the stretch and angular velocities. The theorem of kinetic energy is extended by induction to virtual velocities giving the principle of virtual power. In this framework the power to change the shape is the opposite of the power of the internal forces. The power to change the shape is, in agreement with experiment, null for any rigidifying motion. The resulting equations of motion are volume equations of motion with kinematic and sthenic boundary conditions. This presentation assumes that there are neither defects nor dislocations but it points out where they may intervene.