1 | Entity->tBob += ddtBob*dt*dt + Entity->dtBob*dt; |
However, the actual equations of motion assuming a constant ddtBob applied over a time period of dt would be:
1 | Entity->tBob += ddtBob*dt*dt*0.5 + Entity->dtBob*dt; |
I'm not sure how much difference it makes, I think it's only a second order effect so it's probably pretty small.
By the way, I think using implicit Euler here is a better idea because it's stable for any dt and the equations are not difficult to derive for a simple damped spring.