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 23 lb when the distance is 9 in., find the repulsive force when the distance is 3 in.

Answer 1

f = k/d^2

Where:

f= force

d= distance

k= constant

f= 23 lb

d = 9

d2 = 3

f2 = x

f = k/d2^2

Replacing:

23 = k / 9^2

23= k/ 81

23*81 = k

k= 1863

When d is 3 in

F = 1863 / 3^2

F= 207 lb