A block of mass 5kg is lying on a rough horizontal surface. The coefficient of static and kinetic friction are 0.3 and 0.1 and g=`10 ms^(-2)` The frictional force on the block is

Options

A. 25 N
B. 15 N
C. 10 N
D. zero

Answer

To solve the problem, we need to determine the frictional force acting on a block of mass 5 kg lying on a rough horizontal surface. The coefficients of static and kinetic friction are given, but we need to analyze the situation carefully.

### Step-by-Step Solution:

1. **Identify the Given Data:**
- Mass of the block, \( m = 5 \, \text{kg} \)
- Coefficient of static friction, \( \mu_s = 0.3 \)
- Coefficient of kinetic friction, \( \mu_k = 0.1 \)
- Acceleration due to gravity, \( g = 10 \, \text{m/s}^2 \)

2. **Calculate the Normal Force:**
The normal force \( N \) acting on the block can be calculated using the formula:
\[ N = m \cdot g \]
Substituting the values:
\[ N = 5 \, \text{kg} \cdot 10 \, \text{m/s}^2 = 50 \, \text{N} \]

3. **Determine the Maximum Static Friction:**
The maximum static friction force \( f_s \) can be calculated using the formula:
\[ f_s = \mu_s \cdot N \]
Substituting the values:
\[ f_s = 0.3 \cdot 50 \, \text{N} = 15 \, \text{N} \]

4. **Analyze the Situation:**
Since the problem does not mention any external force acting on the block, we conclude that there is no applied force trying to move the block. Frictional force only arises in response to an applied force.

5. **Conclusion:**
Since there is no external force acting on the block, the frictional force is:
\[ f = 0 \, \text{N} \]

### Final Answer:
The frictional force on the block is \( 0 \, \text{N} \).