Two magnets of same size and mass make respectively 10 and 15 oscillations per minute at certain place. The ratio of their magnetic moment is

Explanation

As the magnets have same size and same mass , their moments of inertia are same .
Let their respective magnetic dipole moments be `M_(1)` and `M_(2)` .
Now , frequency of oscillations of a bar magnet is given as
`f = (1)/(2pi) sqrt((MB)/(I))`
`implies (f_(1))/(f_(2)) = sqrt((M_(1))/(M_(2)))`
`implies (M_(1))/(M_(2)) = (f_(1)^(2))/(f_(2)^(2))`
As `f_(1) = 10` osc/min , `f_(2) = 15` osc/min , we get
`(M_(1))/(M_(2)) = ((10)/(15))^(2) = (4)/(9)`.