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Without thinking too much I attempted an experiment
which failed, as described below. Comments and
suggestions will be appreciated.
I wanted to measure the attractive force between the
poles of two bar magnets (each 13 cm long and 1 cm
in diameter. Keeping these magnets by hand I started
to feel the attraction when the distance between the
coaxially positioned bars was 1 cm or so.)
I suspended one magnet from a brass spring whose
k was 10 N/m. The mass of the spring was 175 g
while the mass of the magnet was 61 g. Naturally,
the spring stretched a little. Then holding another
magnet by hand I started approaching its pole toward
the suspended magnet from below. I expected to see
additional stretching of the spring for each distance
between the poles, for example 1 cm, 0.75 cm and
0.5 cm and 0.25 cm. But this did not happen.
The suspended magnet moved suddenly to the hand-
held magnet to establish the contact (when the distance
between the poles was less than about 1 cm). This
happened regardless of how careful I was in trying
to prevent natural oscillations. What is wrong with
this attempt to measure the magnetic force Fm?
I expected the equilibrium at: k*x=mg+Fm.The
Fm increases when the distance between the poles
becomes smaller and I expected larger x for smaller
distances between the poles. What should I do?
I know that Coulomb used a torsion spring to
establish the relation between Fm and the distance
between the two poles. Why is my linear spring
different? Why was my equilibrium unstable?