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 10 lb when the distance is 16 in., find the repulsive force when the distance is 8 in.
A) 40 lb
B) 60 lb
C) 20 lb
D) 5 lb
E) 2 lb

Question

Quizplus · Accepted Answer

The force is inversely proportional to the square of the distance, so halving the distance (from 16 in to 8 in) increases the force by a factor of 4 (since $16^2 / 8^2 = 4$), making the force 40 lb.

The Repulsive Force (F) Between the North Poles of Two