What happens when a plastic lid sprinkled with iron filings is placed over a magnet?

When a plastic lid is sprinkled with iron filings is placed over a magnet then a pattern is formed. The iron fillings arrange themselves in a way how magnetic field is present. The force of the magnet is the strongest at the two ends because more iron particles are concentrated in these areas. The magnetic lines of flux flow from one end to the other.

force is mass*acceleration.

we have a very small mass: 11.4*0.001 kg

if we want 0.035n of force, we need an acceleration:

0.035 = 11.4*0.001*a

a = 0.035/(11.4*0.001) m/s^2