Value for k

 Hooke's Law - which dates from the 17th century - is a cornerstone on the
study of simple harmonic oscillators. Asking Google to explain it to me in French
brought up course notes from the  Collège Maisonneuve in Montreal (a
junior college with a lot of math students ).

Hooke's law describes the behavior of an ideal string which exerts a certain force
on a mass. It is a vector quantity, which can be plotted on the x axis for convenience.
On the hanging from the ceiling version, one ends up finding the elusive Hooke constant k,
in newtons per meter. Helpful!