Computer Formulation of the Equations of Motion Using Tensor Notation A means is described for extending the area of application of digital computers beyond the numerical data processing stage and reducing the need for human participation in the formulation of certain types of computer problems. By the use of tensor calculus and a computer language designed to facilitate symbolic mathematical computation, a method has been devised whereby a digital computer can be used to do non-numeric work, that is, symbolic algebraic manipulation and differentiation. To illustrate the techniques involved, a digital computer has been used to derive the equations of motion of a point mass in a general orthogonal curvilinear coordinate system. Since this operation involves a formulation in terms of first- and second-order differential coefficients, it provides a good demonstration of a computer's capability to do non-numeric work and to assist in the formulation process which normally precedes the numerical data processing stage. Moreover, this particular problem serves to illustrate the advantages of the mathematical techniques employed. With the program prepared for this purpose the computer will derive the equations of motion in any coordinate system requested by the user. Results are presented for the following coordinate systems: cylindrical polar, spherical polar, and prolate spheroidal. CACM September, 1967 Howard, J. C. CA670903 JB February 27, 1978 3:58 PM 1543 4 1543 1543 4 1543 1664 4 1543 1664 4 1543 1345 5 1543 1543 5 1543 1543 5 1543 1543 5 1543 1616 5 1543 1664 5 1543 1345 6 1543 1543 6 1543 1616 6 1543