Limiting value of static frictional force on a block placed on the rough surface depends on

Options

A. Nature of surfaces in contact
B. Area of surfaces in contact
C. Normal reaction
D. Both (1) & (3)

Answer

To determine the limiting value of static frictional force on a block placed on a rough surface, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Static Friction**:
- Static friction is the force that opposes the initiation of motion between two surfaces in contact. The maximum value of static friction is referred to as limiting friction.

2. **Formula for Limiting Friction**:
- The limiting frictional force (F_s) can be expressed mathematically as:
\[ F_s = \mu_s \cdot N \]
- Where:
- \( F_s \) = Limiting static frictional force
- \( \mu_s \) = Coefficient of static friction (depends on the nature of the surfaces in contact)
- \( N \) = Normal force (the perpendicular force exerted by a surface on an object in contact with it)

3. **Factors Affecting Limiting Friction**:
- The limiting friction depends on:
- **Nature of the surfaces**: Different materials have different coefficients of static friction. For example, rubber on concrete has a higher coefficient than wood on wood.
- **Normal force (N)**: The greater the weight of the object (which affects the normal force), the greater the limiting friction. For a block resting on a horizontal surface, \( N \) is equal to the weight of the block, which is \( mg \) (mass times gravitational acceleration).

4. **Conclusion**:
- Therefore, the limiting value of static frictional force on a block placed on a rough surface depends on both the nature of the surfaces in contact and the normal force acting on the block.

### Final Answer:
The limiting value of static frictional force depends on:
- The nature of the surfaces (coefficient of static friction, \( \mu_s \))
- The normal force (N)