Given forces \( F_1 = 2 \, \text{N} \) and \( F_2 = 16 \, \text{N} \), and a rod length of 21 cm, the point where the resultant force acts can be determined using:
\[\nx = \frac{F_2 \times d_2}{F_1 + F_2}\n\]
Where:
- \( F_1 = 2 \, \text{N} \), \( F_2 = 16 \, \text{N} \)
- \( d_2 = 21 \, \text{cm} \)
Substituting the values:
\[\nx = \frac{16 \times 21}{2 + 16} = \frac{336}{18} = 18.67 \, \text{cm}\n\]
The distance from the greater force (16 N) is \( 18.67 \, \text{cm} \). The correct answer is 4 cm.