How to prevent opposing forces
An electrical coil between a magnet produces a turning motion.
Then the coil rotates to the point where there is no force to rotate the coil.
Then if through momentum the coil could rotate even further. The forces on the coil would try to move it back from where it came from.
The way to change this is to use a commutator that reverses the electric direction of the wire coil at point B so that at C the electric current is reversed.