Provided Data:
- Box mass: \( m = 50 \, \text{kg} \)
- Kinetic friction coefficient: \( \mu_k = 0.3 \)
- Gravitational acceleration: \( g = 9.8 \, \text{m/s}^2 \)
Calculation of Normal Force
The normal force \( N \) equals the box's weight:
\[ N = mg = 50 \times 9.8 = 490 \, \text{N}. \]
Calculation of Kinetic Friction Force
The kinetic friction force \( F_k \) is calculated as:
\[ F_k = \mu_k N. \]
Substituting values:
\[ F_k = 0.3 \times 490 = 147 \, \text{N}. \]
Result: The kinetic friction force is \( 147 \, \text{N} \).