Is it odd that I’m stroking it rn in circular motion, the periodic motion of my hand acts as centripetal force but it’s from the side view so instead of looking like I’m going in circles, it looks like I’m going side to side like simple harmonic motion. It’s stated that simple harmonic motion is when an object’s acceleration is proportional to the negative of its displacement. Resultant force in a linear plane is defined as the rate of change of momentum or F=ma. The fact that I’m constantly changing direction while stroking in circular motion means that my speed might be the same but I’m actually accelerating since I’m changing direction- changing my velocity. Velocity is a vector based on magnitude and direction.