I loved the SHM number plate. SHM in Physics is Simple Harmonic Motion. It is basically oscillatory motion like a mass bouncing up and down on a spring. The definition states that during the motion, the acceleration is always proportional to the displacement from equilibrium and that the acceleration is always directed towards equilibrium. In English, this means that if you pull a mass on a spring twice as bar from its natural length, its acceleration will be twice as big and pulling towards the middle. In the middle, the acceleration will be zero but its momentum will carry it through. Above the middle, it keeps going up but the acceleration will be pulling back down towards the middle.
