This term is negative in both exothermic and endothermal equations. As shown in Fig. , in the exothermic process, < 0, thus, A donates a positive force to B. Inversely, in the endothermal process, B records accepting an opposing force from A. It is similar to the asymmetric situation discussed above, but as shown in Fig. , they are contract forces in liquid. We cannot imagine that A will rotate around B in a dense liquid and solid. However, resembling the terms in Eq. 19 and Eq. 22, it can be concluded that the property of force is rotational. Since Eq. 18 succeeds in predicting equilibrium distance, it is expected that Eq. 29 is suitable for predicting the properties of liquid and solid, which most MD simulations work for - . For example, the liquid droplets spontaneously deform into spheres suspended in the atmosphere. Conventional mechanics attributes the spherical shape to the unbalanced molecular interactions of surface molecules or cohesive forces, stating that the droplets simultaneously deform their shapes with the smallest surface area to decrease the surface/interfacial tension. However, this explanation is not convincing due to the many exceptions. For example, the interfacial tensions of water-air, benzene-air, and ethanol-air are 72.75, 28.88, and 22.39 mN/m at 293.17 K. It is hard to believe that the molecular interactions in benzene are more potent than the hydrogen bonds in ethanol. Moreover, the interfacial tension is practically zero in the atmosphere of liquid-gas saturation. Hence, Eq. 29 gives the driving force of deformation but weakly relates to the surface tension . Moreover, Eq. 29 reasons that the vortices are prevalent in the fluidic flows , . In summary, the forces created by collision are symmetrical, whereas the forces produced by temperature variation gradient and volumetric variation gradient are asymmetric. The symmetric forces create the linear motion, while the others create the spin or rotation. These disclose the essence of forces and the origins of various motions, such as spin and rotation, which are popular models in the cosmos. All equations solve Newton's "causes hitherto unknown." The origin of force is heat transfer, which doesn't need a medium for the force transfer. These results indicate that the definition of heat is appropriate, and by this definition, the new thermodynamics integrates classical mechanics well.