Kinetic Friction: Overview, Questions, Preparation

The force that acts between the two moving surfaces is known as Kinetic Friction. The force acting on a surface and the body moving on the surface both experience an opposite direction of its movement. The magnitude is dependent on the Kinetic Friction of the objects.

Kinetic friction is further divided into three types:

1. Sliding Friction
2. Rolling Friction
3. Fluid Friction

‘mu’ is the coefficient of kinetic energy. It is denoted as μ with a subscript k. the force is expressed in Newtons (N). The kinetic force is μk times the normal force. The formula of kinetic energy can be written as:

F_k = μ_k n

Here, the F_k is the kinetic frictional force

μ_k is the coefficient of kinetic friction

n is the normal force

The friction is categorised into two types which are explained below:

1. Static Friction
2. Kinetic Friction

Static friction occurs between the two non-moving objects. The resistance that occurs in liquids between the two objects is called Viscosity. On the other hand, the friction that occurs between the two moving objects Is known as kinetic friction.

The static energy is represented as F_s = μ_s n. The magnitude of static friction is greater than the kinetic friction because of the high value of its coefficient, and the magnitude of the kinetic friction is low as the value of its coefficient is low.

The applications of the kinetic friction are listed below:

1. It is used in our everyday life while we rub any two objects together
2. It is used for the wear and tear of the objects
3. When we rub objects together, it produces friction that gives rise to fire
4. The thermal energy is generated when the two objects are rubbed with each other, and it is caused by friction

Kinetic friction for Class 12

The chapter 'Friction' holds a weightage of a significant 14 marks. The chapter is very important as per the new pattern of 2021. It includes six questions in total, consisting of two objective type questions, two very short questions, one short, and one long question.

Example 1) Write the types of Kinetic Friction.

Answer – Kinetic friction is divided into three types:

1. Sliding friction
2. Rolling friction
3. Fluid friction

Example 2) Write examples of Kinetic Friction.

Answer – The kinetic friction includes a person sliding down a slide, a book sliding against the table, a child sliding down a slide, iron being pushed down across the cloth material, etc.

Example 3) Write examples of Static Friction.

Answer – The paper on the table, bookmark on the book, car parked on a hill are all examples of Static friction.

Q: What do you mean by Kinetic Friction?

Q: What are the applications of Kinetic Friction?

Q: Write the types of Friction.

Q: What is Static Friction?

Q: What is the unit of the coefficient of Friction?