˙ ? ? ? ? ? ? ++++ ++++ ++++ ++++ ++++ Concept Question ++++ ++++ ++++ ++++ ++++ Which of the following expressions represents the rate of work done by the stresses during the deformation of a body of an arbitrary material? V ?u ?t ?u ?t dS + f · dV (1) t · S S V ?u ?t ?u ?t (n · σ) · dS + f · dV (2) V σ ij ? ij dV (3) V 1 2 ?u ?t · ?u ?t dS (4) ρ 1. ++++ Eqn.(1) 2. ++++ Eqn.(2) 3. ++++ Eqn.(3) 4. ++++ Eqn.(4) 5. ++++ DKDU ++++ ++++ ++++ ++++ ++++ Answer ++++ ++++ ++++ ++++ ++++ The correct answer to the concept question is: 3. ++++ Eqn.(3).