The Science of Spanking

For some people, a spanking is nothing more than a painful punishment. But for the rest of us, a good spanking can be some combination of restorative, sexy, spiritual, communicative, sensual, thrilling, reaffirming, therapeutic, and redemptive. I love everything about it. In this spirit, this post examines the physics of bottom warming.

Let’s consider what happens when a flat, rigid paddle makes forcible contact with a spankee’s bottom. The paddle, swung by a spanker, acquires momentum. We can define momentum (p) as mass (weight) times velocity.

p = mv

In this equation, we can observe that momentum increases when mass increases (such as when a heavier paddle is used) or when velocity increases (when the paddle is swung faster). It occurs to me that what I perceive as harder swats are actually those where the implement is traveling faster.

This velocity component also explains why a spankee’s right cheek marks more and hurts more after a paddling from a right handed spanker. As the paddle is swung in an arc, the far end of a paddle moves faster, travels farther, and imparts more momentum than the end closer to the handle.

Upon impact, the paddle’s momentum is transferred to the spankee’s (mostly) stationary bottom. This momentum is absorbed by the bottom and the surrounding soft tissue. I used to wonder how I could get marks in places where I was fairly certain I wasn’t hit. After a particularly thorough paddling, I would notice dark vertical bruises on either side of my crack or horizontal bruises very high up on my cheeks. How could that happen?

The answer lies in the way the that body dissipates the momentum transferred from a paddle or similar implement. When a bottom is struck, it compresses and then snaps back. However, as illustrated in this slow motion video from Michael Masterson, the impact generates displacement waves that spread far beyond the spot of impact. Both hips and thighs are affected.

There is one other aspect we should explore. A large implement, like the paddle we considered above, transfers its momentum to a fairly broad impact area (yes, I know, broader in my case), but what about an implement like a hairbrush or bath brush where the impact area is smaller? Our momentum formula suggests that the lesser weight of a light implement can be offset by higher velocity. But the size of the impact zone also affects the spankee’s experience. A smaller implement concentrates the transfer of momentum, and therefore the damage and the pain. Anyone who has been spanked with a bath brush can attest to this phenomenon.

So next time you’re lying across someone’s lap (or have someone over your lap), I invite you to give a quick thought to the transfer of momentum. Science can be fun when spankings are involved!

Please stay safe everyone.