Two bar magnets of length 0.1m and pole strength 75 Am each are placed on the same line.The distance between their centres is .2m.What is the resultant force due to one on the other when
(1)the north pole of one faces the south pole of the other
(2)the north pole of one faces the north pole of the other
Magnetic Moment = M = Pole Strength x Length of the Magnet
M = mL = 75Am x 0.1m = 7.5Am2
If the opposite poles of two magnets face each other the field due to M1 (magnet -1)at the position of M2 (magnet -2)will be
If the similar poles of the two magnets face each other θ = 1800 and so U and F will be positive.
10^-7 * 2 * 75 * (0.1) d / (d^2 - 0.1^2)^2
One pole is at a distance of 15 cm and the other pole is at a distance of 25 cm
So we have to find the forces on 75 Am one attractive and the other repulsive.
With these two we have to find the resultant. Hope you would find it on your own.