I'm a fan of computer keyboards, and I was thinking about the durability of electrical contacts that lay below the keys on certain kinds of keyboards, such as this one.
I tried to wonder how many keystrokes that a PCB could take before wearing down, but then it occurred to me that a normal keystroke, as in, pressing down on the key until the key buckles and taps down on the PCB, seems like it'd do a lot more wear than starting with the key down on the PCB, and then pressing down.
Intuitively, I know that doing the "up-down" keystroke has more impact on the PCB, but since you could exert more force with the "down-down" press, with the key starting directly on the PCB, I can't figure out how the first one is supposed to have more impact.
I figured that the "down-down" press would transfer the force through the key, through the PCB, through the keyboard base, through the table into the ground, but I figured that the "up-down" press does the same thing. What's responsible for the latter having more of an impact on the PCB, assuming that the resulting force of the accelerating pressing finger is the same as the non-accelerating pressing finger over time?