Newton's second law (equations 10.1, p. 492 and 10.4, p. 495) are all that are needed to solve any dynamic force system by the newtonian method. Jean le Rond d' Alembert (1717-1783), a French mathematician, rearranged Newton's equations to create a "quasi-static" situation from a dynamic one. D' Alembert's versions of equations 10.1 and 10.4 are: