Calculate the force acting between two magnets of length `15cm` each and pole strength `80Am` each when the separation between their north poles is `10cm` and that between south poles is `40cm`.

Explanation

The given situation is shown in figure.

Here, `m_1=m_2=80Am`
Force of attraction between `N_1` and `S_2`
`F_1=(mu_0)/(4pi)(m_1m_2)/(r^2)=10^-7xx(80xx80)/((0*25)^2)`
`=0*01024N`
Force of attraction between `N_2` and `S_1`
`F_2=(mu_0)/(4pi)(m_1m_2)/(r^2)=F_1=0*01024N`
Force of repulsion between `N_1` and `N_2`
`F_3=(mu_0)/(4pi)(m_1m_2)/(r^2)=10^-7xx(80xx80)/((0*1)^2)=0*064N`
Force of repulsion between `S_1` and `S_2`
`F_4=(mu_0)/(4pi)(m_1m_2)/(r^2)=10^-7xx(80xx80)/((0*40)^2)=0*004N`
`:.` Resultant force between the two magnets
`F=F_1+F_2-F_3-F_4`
`=0*01024+0*01024-0*064-0*004`
`=-0*04752N`
`F=-0*048N` (minus sign for repulsion).