  Spicules and other solar jets such as bright points and fibrils generally
show a parabolic height-time relationship, which means that each spicule has a
constant deceleration. However the deceleration is only constant for a
particular spicule and varies widely from one spicule or jet to another.
Nonetheless the careful observations of a number of researchers show that the
distance - time relationship is parabolic to a high level of precision. The
measurements for heights, maximum velocities, decelerations and flight times
are normally presented as histograms or scatter plots, which allow some general
trends to be observed. The published results show a clear correlation between
the maximum velocity and the deceleration of spicules on scatter plots. This
correlation has been claimed to show a linear relation between the acceleration
and the maximum velocity of a jet. This linear relationship has been used to
help model the mechanisms responsible for the jets. However it is proposed here
that the relation between velocity and acceleration is given by the normal
equations of motion for constant acceleration and consequently the relationship
is non-linear. Other correlations are also examined and the implications for
spicule mechanisms are considered.
