The surface tension of water is 72 dyne//cm. Express is in SI units.

Explanation

To convert the surface tension of water from CGS units (dyne/cm) to SI units (N/m), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Value and Units**:
The surface tension of water is given as 72 dyne/cm.

2. **Understand the Conversion Factors**:
- 1 dyne = \(10^{-5}\) Newton (N)
- 1 cm = \(10^{-2}\) meter (m)

3. **Set Up the Conversion**:
We need to convert dyne/cm to N/m. Using the conversion factors:
\[ \text{Surface Tension (in N/m)} = \text{Surface Tension (in dyne/cm)} \times \left(\frac{10^{-5} \text{ N}}{1 \text{ dyne}}\right) \times \left(\frac{1 \text{ cm}}{10^{-2} \text{ m}}\right) \]

4. **Substitute the Values**:
Substitute the known values into the equation:
\[ \text{Surface Tension (in N/m)} = 72 \, \text{dyne/cm} \times \left(\frac{10^{-5} \text{ N}}{1 \text{ dyne}}\right) \times \left(\frac{1 \text{ cm}}{10^{-2} \text{ m}}\right) \]

5. **Simplify the Expression**:
\[ = 72 \times 10^{-5} \text{ N} \times \frac{1}{10^{-2} \text{ m}} \]
\[ = 72 \times 10^{-5} \text{ N} \times 100 \text{ m}^{-1} \]
\[ = 72 \times 10^{-3} \text{ N/m} \]

6. **Final Result**:
The surface tension of water in SI units is:
\[ 72 \times 10^{-3} \text{ N/m} \text{ or } 0.072 \text{ N/m} \]