# Oscillation of a bar magnet

1. Oct 26, 2009

### Marcstylzzz

Please help, if a magnet is displaced from its equilibrium position by a small angle (theta), show that it will oscillate with a period T given by T= 2*pi*sqrt(I/mB)
I = moment of inertia of the bar magnet and equals M(L^2 + a^2)/12
B = earths horizontal component of magnetic field
M is the mass
L is the length and a its width

2. Oct 26, 2009

### Gear300

Is the magnet you're referring to oscillating like a compass needle does (the period they gave looks a lot like the period for the physical pendulum)?

If that is the case, then suitable method would be to find a way to write out an equation displaying SHM (much like the pendulum with oscillations of small angles). A good way of deriving it would probably be using torque (tau) as tau = I*@, in which I is moment of inertia and @ is angular acceleration.

Last edited: Oct 26, 2009