In a simple model we can describe the walking pace of a person in terms of a
physical pendulum. We model the human leg as a solid rod that pivots from the
hip. Furthermore, when we walk we do so at a comfortable pace that coincides
with the natural period of oscillation of the leg. If we assume a value of 0.8 m for
l, the length of the leg, then its natural period is ∼1.5 s. One complete period of
the swinging leg corresponds to two strides. Try this yourself. If the length of a
stride is, say, 1 m then we would walk at a speed of approximately 2/1.5 m s−1
which corresponds to 4.8 km h−1 or about 3 mph which is in good agreement with
reality.