The repulsive force f between the north poles of two magnets is inversely proportional to the square of the distance d between them.

Question

The repulsive force f between the north poles of two magnets is inversely proportional to the square of the distance d between them. If the repulsive force is 21 lb when the distance is 6 in., find the repulsive force when the distance is 2 in.

Answer 1

So Kevin C.,

Ratio those two distances you are given: 2 in. and 6 in. That ratio is 3. Square that value to obtain the force ratio factor. Since you are placing the magnets CLOSER than the initial data condition, multiply the initial force by the force ratio factor, to get your result.

Note: this force will only apply, when the two poles are directly (in a straight line) opposed. If you are at any other angle to the N-S centerline of the magnets, it probably won't be an inverse square relationship.

-- Cheers, -- Mr. d.