Correct Option
The correct option is (c) 1 and 3 only.
Explanation
Friction is a contact force that resists the relative motion or tendency of such motion of two bodies in contact. It arises due to electromagnetic interactions between the atoms and molecules of the surfaces in contact, manifesting as interlocking of surface irregularities.
Statement-wise Analysis
- Statement 1 is Correct: Friction always acts in a direction opposite to the direction of relative motion between the two surfaces. If a body moves to the right on a surface, the frictional force acts to the left to oppose that motion.
- Statement 2 is Incorrect: The force of friction is strongly dependent on the nature of the two surfaces in contact (e.g., their roughness, smoothness, and material composition). While friction is generally independent of the area of contact (for macroscopic bodies), it varies significantly based on whether the surfaces are rough or polished.
- Statement 3 is Correct: Friction cannot be eliminated completely in practical situations. Even surfaces that appear smooth to the naked eye possess microscopic irregularities. When two surfaces touch, these irregularities interlock, and molecular bonds (cold welding) form at the points of contact, ensuring that some frictional force always exists.
Key Takeaway: Friction is a non-conservative force that opposes relative motion. Its magnitude depends on the nature of the surfaces in contact and the normal force, but it can never be reduced to zero in practical mechanical systems.