কাইনেটিক ফ্ৰিকশন

Kinetic Friction

Definition

• Kinetic friction: the force that opposes motion between two surfaces that are already in contact and sliding against each other.

Characteristics

• Kinetic friction is always parallel to the surface in contact.
• Kinetic friction always opposes motion.

Factors Affecting Kinetic Friction

• Normal Force (Fn): increased normal force increases kinetic friction.
• Surface Roughness: increased surface roughness increases kinetic friction.
• Surface Area: increased surface area in contact increases kinetic friction.
• Velocity: kinetic friction is independent of velocity (at low velocities).

Kinetic Friction Coefficient (μk)

• Definition: ratio of kinetic friction force (Fk) to normal force (Fn).
• Formula: Fk = μk * Fn.
• Values: varies depending on the surfaces in contact (e.g., μk = 0.1 for steel on steel).

Examples and Applications

• Braking systems: kinetic friction is used to slow down or stop moving objects (e.g., car brakes).
• Machine components: kinetic friction affects efficiency and wear in moving parts (e.g., gears, bearings).
• Sports: kinetic friction affects athlete performance (e.g., friction between shoes and track).