Force between two identical bar magnets whose centres are r metre apart is `4.8 N`, when their axes are in the same line. If separation is increased to `2r`, the force between them is reduced to

Options

A. 2.4N
B. 1.2N
C. 0.6N
D. 0.3N

Answer

D

Explanation

`F prop (1)/(r^(4))`
`rArr (F_(1))/(F_(2))= ((r_(2))/(r_(1)))^(4)= (2)^(4) = 16 rArr F_(2)= (4.8)/(16)= 0.3N`