Substituting equation (3.21) into equation (3.22).

                                                                                   (3.23)

The term outside the bracket in RHS is an exponentially decaying function. The term

can have three cases.

(i) : exponents in equation (3.23) will be real numbers.

• No oscillation is possible as shown in Figure 3.3.
• This is an overdamped system (Figure 3.3).