You don't feel any weight because your weight is the opposition you get to falling through the floor; but if the floor is giving way and you're just falling freely, you feel weightless.

你不会感到重力,是因为你的重力在阻碍你穿过地板,如果没有地板,你自由下落,也感觉不到重力

耶鲁公开课 - 基础物理课程节选