Examples:

1. Which of the following are ordinary differential equations?
   a. $\frac{dy\left(t\right)}{dt}=\lambda y\left(t\right)$
   b. $\frac{d^{2}y\left(t\right)}{d{t}^2}+{\omega }^{2}y\left(t\right)=f\left(t\right)$
   c. $\frac{dy\left(x,t\right)}{dt}-D\frac{d^{2}y\left(x,t\right)}{d{x}^2}+{\omega }^{2}y\left(x,t\right)=f\left(x,t\right)$
   

   a. $\frac{dy\left(t\right)}{dt}=\lambda y\left(t\right)$ YES, linear first order ODE
   b. $\frac{d^{2}y\left(t\right)}{d{t}^2}+{\omega }^{2}y\left(t\right)=f\left(t\right)$ YES, linear second order ODE, "wave equation"
   c. $\frac{dy\left(x,t\right)}{dt}-D\frac{d^{2}y\left(x,t\right)}{d{x}^2}+{\omega }^{2}y\left(x,t\right)=f\left(x,t\right)$ NO, linear partial differential equation, "time dependent or transient diffusion equation"
   

2. What is the solution of an ODE?
   A function
3. Give two examples of common engineering subjects that involve the solution of ODEs.
   Radiactive decay
   Chemical kinetics
   Mechanics (dynamics)
   Control theory
   Population dynamics
   Diffusion
   Transient electrical circuits