1. **State the problem:** The equation of continuity in fluid dynamics expresses that the mass flow rate must be constant from one cross-section to another in a steady flow. Mathematically, it is given by $$A_1 v_1 = A_2 v_2$$ where $A$ is the cross-sectional area and $v$ is the velocity of the fluid. 2. **Explain the equation:** This means if the area decreases, the velocity must increase to keep the flow rate constant, and vice versa. 3. **Intermediate work:** Suppose we know $A_1$, $v_1$, and $A_2$. To find velocity $v_2$ at the second point, rearrange the equation: $$v_2 = \frac{A_1 v_1}{A_2}$$ 4. **Example:** If $A_1 = 2 \text{ m}^2$, $v_1 = 3 \text{ m/s}$, and $A_2 = 1 \text{ m}^2$, then $$v_2 = \frac{2 \times 3}{1} = 6 \text{ m/s}$$ 5. **Summary:** The equation of continuity ensures fluid conserves mass flow rate by adjusting velocity when cross-sectional area changes. Final answer: $$v_2 = \frac{A_1 v_1}{A_2}$$