(A) : The viscous force, air resistance etc., are examples of contact force
(R) : Contact force on an object arises due to contact with some other object

Options

A. Both (A) and (R) are true and (R) is the correct explanation of (A)
B. Both (A) and (R) are true and (R) is not the
C. (A) is true but ( R) is false
D. Both (A) and (R ) are false

Answer

To solve the question, we need to analyze the assertion (A) and the reason (R) provided:

**Assertion (A)**: The viscous force, air resistance, etc., are examples of contact forces.
**Reason (R)**: Contact force on an object arises due to contact with some other object.

### Step-by-Step Solution:

1. **Understanding Contact Forces**:
- Contact forces are forces that arise when two objects are in physical contact with each other. Examples include friction, tension, normal force, air resistance, and viscous force.

2. **Analyzing the Assertion (A)**:
- The assertion states that viscous force and air resistance are examples of contact forces.
- Viscous force occurs when layers of fluid are in contact and moving relative to each other. Thus, it is indeed a contact force.
- Air resistance (or drag) occurs when an object moves through air, and the air molecules exert a force on the object due to contact. Therefore, air resistance is also a contact force.
- Conclusion: The assertion (A) is **true**.

3. **Analyzing the Reason (R)**:
- The reason states that contact force on an object arises due to contact with some other object.
- This definition aligns perfectly with the concept of contact forces, as they are defined by the interaction between two bodies in contact.
- Conclusion: The reason (R) is also **true**.

4. **Determining the Relationship**:
- Since both the assertion (A) and the reason (R) are true, we need to check if R is the correct explanation of A.
- The reason explains why viscous force and air resistance are classified as contact forces, as they arise from the interaction of objects in contact.
- Conclusion: R is indeed the correct explanation of A.

5. **Final Conclusion**:
- Both assertion (A) and reason (R) are true, and R is the correct explanation of A. Therefore, the correct option is: **Both A and R are true and R is the correct explanation of A**.