# Kinetic Friction, Details About Kinetic Friction, Types of Friction (For CBSE, ICSE, IAS, NET, NRA 2022)

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# Kinetic Friction

• It is the Resistance of a Surface to an Object the Instant It Starts Moving.
• When Two Surfaces Are Moving with Respect to One Another, the Frictional Resistance is Almost Constant over a Wide Range of Low Speeds, and in The Standard Model of Friction the Frictional Force is Described by the Relationship below.
• The Coefficient is Typically Less Than the Coefficient of Static Friction, Reflecting the Common Experience That It is Easier to Keep Something in Motion Across a Horizontal Surface Than to Start It in Motion from Rest.

• Definition: A force that acts between moving surfaces. A body moving on the surface experiences a force in the opposite direction of its movement. The magnitude of the force will depend on the coefficient of kinetic friction between the two materials.
• Friction is defined as the force that holds back a sliding object.
• The kinetic friction is a part of everything and it interferes motion of two or more objects.
• The force acts in the opposite direction to the way an object wants to slide.
• If a Bus has to stop, we apply brakes and that is exactly where the friction comes into play.
• But when we have to stop in the middle of a puddle, things get harder since friction is less there and cannot aid one so much.

## Kinetic Friction Formula

• The coefficient of kinetic friction is denoted by the Greek letter μ, with a subscript “k.”
• The force of kinetic friction is times the normal force on a body.
• It is expressed in Newtons (N) .
• The kinetic friction equation can be written as:
• Force of kinetic friction = (coefficient of kinetic friction) (normal force)

Where,

• = force of kinetic friction
• = coefficient of kinetic friction
• = normal force (Greek letter “eta” )

## Types of Friction

• Static Friction
• Kinetic Friction

### Static Friction

• It is the one present between two objects that are not moving with respect to each other.
• In liquids, friction is the resistance between moving layers of a fluid better known as viscosity.

### Kinetic Friction

• Now take two moving solid objects, this is known as moving or kinetic friction due to its motion.
• It is a particular fraction of the perpendicular force acting between two bodies.
• A coefficient of friction determines the fraction which in turns determined through experiments.
• The force is independent of the contact area and doesn՚t change no matter how fast the two objects are moving. In other scenario, static friction is what affects stationary objects.
• The force of friction is a force that resists motion when two objects are in contact.

## Applications of Kinetic Friction

• It plays a huge role in everyday occurrences like while rubbing of two objects takes place. The resulting motion converts into heat and thus resulting in the fire in some instances.
• For wear and tear and that՚s why we need oil to lubricate machine parts, as it reduces friction.

## Difference between Static Friction and Kinetic Friction

 Static Friction Kinetic Friction It is the friction present between two or more objects that are not moving with respect to each other It is the friction present between two or more objects that are in motion with respect to each other. The magnitude is greater due to the greater value of its coefficient The magnitude is comparatively lesser due to the low value of its coefficient

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