Physical common sense is the intuitive knowledge that can be obtained from the physical world. But the common sense will be broken in symmetrical reality because of the integration of the physical world and the virtual world. In this paper, we will introduce the specific physics in symmetrical reality from two perspectives, i.e., existence and interaction. We emphasize the bi-directional mechanical control within the symmetrical reality framework and why free wills of machines can break the common sense. Afterward, we give the experiments of discovering the new physical common sense of symmetrical reality systems. Experiment I is about learning physical common sense from symmetrical reality, which is used to show what can be learned and how to learn in a symmetrical reality environment. Experiment II is about changing the physical common sense of symmetrical reality, which is used to show why physical common sense deserves much attention. Finally, we draw an initial conclusion about the physical common sense in symmetrical reality and give some suggestions for understanding symmetrical reality-based physical common sense.