Here you go, Piston area and force.

OK,
I apologise for using the word dummies.
This 'discussion' started because 273 claimed that more piston area gave more hp by virtue of the piston area increase. It only does this IF more air is drawn into the cyl; if no more air was drawn into the cyl, then the HP would not change, all else being equal.

THIS FORMULA SPECIFICALLY ADDRESSES EXACTLY WHAT IS BEING DISCUSSED. What do you not understand about Power per piston area???