Question

the force of attraction between two magnets is inversely proportional to the square of the distance between them. when the magnets are r cm apart, the force of the attraction between is F newtons (N). if the distance between the magnets is increased by 400%, the force of magnets between them becomes cF N . Find the value of c.​

Answer 1

The force of attraction between 2 magnets is inversely proportional to it's distance squared.

That means

$f = \frac{1}{ {r}^{2} }$

so when the magnets are 4 times apart the resultant force is divided 8 times.

So,

$\frac{f}{8} = \frac{1}{8} f$

We can see here C=1/8.