I did not answer well this one. This was a good opportunity to impress them. If you want to impress them, answer with "It is a field of study that deals with output behavior of physical bodies when subjected to inputs of force, torque, pressure, displacements, electric/magnetic/gravitational fields, and usually involves geometrical and time varying aspects of motion (if the body moves), or stresses/deformations (if the body does not move when subjected to these inputs). The output behavior may be described in terms of descriptors of motion, stress profiles, or deformations and how they vary with time. It is divided into two subfields of a) kinematics, which studies motion without regards to forces which cause them, and involves only geometrical aspects and their time derivatives like position, velocity, acceleration, angular diaplacent, angular velocity, angular acceleration, without involving properties of matter like mass, moment of inertia or the causes of motion/deformation like Forces/torques etc. And b) dynamics which studies the causes of motion/stresses/deformations which includes Force/Torque/Pressure/Electrical, Magnetic, Gravitational fields or properties of matter like mass, moment of inertia etc."