How Do You Know if You're Going at 60 Hurs?

We drew a dot on the ball. And we are also given a strobe light, where you can control how fast the light was flashing. Now remember how i said the ball was magnetized and the moment of the of the ball is going around at 60 hurts? So what happens is that you need to lock the rotation of the ball to the current. Once it goes at 60 hurts, once it's not moving at all, then you know that it's exactly at 60 herts. The reason why it doesn't slow down is because when the magnetic field is going from down to up, the Magnetic Field pushes the moment upwards.