Why people raise their hand when they knock a door?

Question

Because you can knock a door with your hand down as well and it would be more convenient?

In: Physics

Answer 1

Have you actually tried knocking on a door with your hand down or are you just basing this question based on the showerthought that showed up a couple of days ago?

Yeah you can do it, but it’s nowhere near as convenient and you can’t knock nearly as hard/well with your hand in the below position and depending on how sensitive your joints are it actually hurts a bit knocking on the door from below then it does from above because you use your MCP joints to knock from below which are more sensitive, instead of your PIP joints.