MECHANICAL WORK, ENERGY, AND POWER - Biomechanics and Motor Control of Human Movement - page 148

Figure 6.7 Forces, velocity, mechanical power, and work done on a baseball while
being thrown. See the text for details.
calculated. When the baseball is caught, the force of the hand still acts against
the baseball, but the velocity is reversed. The force and velocity vectors are
now in opposite directions. Thus, the power is negative and the work done
is also negative, indicating that the baseball is doing work on the body.
6.0.9 Mechanical Energy Transfer between Segments
Each body segment exerts forces on its neighboring segments, and if there is
a translational movement of the joints, there is a mechanical energy transfer
between segments. In other words, one segment can do work on an adja-
cent segment by a force displacement through the joint center (Quanbury
et al., 1975). This work is in addition to the muscular work described in
Sections 6.0.4 to 6.0.7. Equations (6.5) and (6.6) can be used to calculate
the rate of energy transfer (i.e., power) across the joint center. Consider the