This paper provides a new perspective to understand existing controversy on the social force model. These issues include that the social force disobeys Newton 3rd Law, oscillation phenomenon when one agent is approaching another as well as some questions on the faster-is-slower effect. From the perspective of physics these problems seem difficult to explain. This paper provides a new perspective to understand these issues. We introduce a new concept of desired interpersonal distance to explain how the social force is generated from conscious mind of human. Although the social force disobeys Newton 3rd Law, the whole model is exactly within the Newton Laws to characterize pedestrian motion. The oscillation phenomenon may exist in non-physics entity (i.e., desired velocity and desired interpersonal distance) rather than physics entity (i.e., actual velocity and actual distance), and such oscillation is mitigated by treating non-physics entity as variable rather than constant. Very interestingly, the desired velocity represents the motivation level of pedestrian motion, and the faster-is-slower effect is thus explained by Yerkes–Dodson law, explaining how motivation level could improve or impair human performances in a collective sense. This inverted-U effect is further studied with a falling-down model and the numerical testing is exhibited by using FDS+Evac.