How To Find Friction Force Without Coefficient: Detailed Explanations And Problem Examples

This article answers the question- how to find friction force without coefficient. We all are familiar to friction and must have experienced friction everyday in our daily lives.

We also know that it requires co efficient of friction in order to calculate the magnitude of frictional force. But what happens when we do not know the value of co efficient of friction and we still need to find the magnitude of frictional force? We shall study that in this article.

What is friction?

We all aware of friction and its effect on our daily lives. We cannot walk or run without the help of friction. Even though it is the opposing force, it helps us to move forward.

The resistance to our motion is called as friction. The friction arises due to simple irregularities on the surface of the objects. Nothing in this world is ideal and so is not any surface. There has to be at least some irregularities which will give rise to the friction.

how to find friction force without coefficient
Image: Friction taking place between two surfaces

Image credits: CaoHaoFriction between surfacesCC BY-SA 4.0

What is co efficient of friction?

Co efficient of friction is the ratio between the frictional force to the normal reaction force acting on the object.

It is used to find the value of force due to friction. This co efficient also tells us the value of roughness present on the surface. Simply put, co efficient of friction is a measure of how rough a surface is and makes it easy for us to find the magnitude of frictional force.

How to find the value of friction without coefficient?

Without the co efficient of friction’s value in hand we cannot find the force of friction. The co efficient of friction can be found using two different methods.

One is very simple, we can simply check the standard values from a textbook. The standard values of different materials are listed in a book of standard values. Other way to find out the co efficient of friction is by experimentation. For an inclined plane the tan of angle of inclination gives the value of co efficient of friction.

Applications of friction

Friction is not always bad. It is used in many applications that we shall see in the list given below-

  • Walking– Walking makes the best use of friction. Without friction, the human body would have stayed at one place struggling to move forward. This is because while walking, forward reaction gives a major push to our body which helps us in moving forward.
  • Running – Running is a successor to walking. If we run on a treadmill we do not move forward. This is due to the fact that the treadmill will go backward at the same speed. In case of a smooth road, the body will not get enough forward reaction force to move forward hence the body will keep running at the same spot like on treadmill.
  • Driving – Driving is an another important application of friction. The wheels of car undergo immense friction which is responsible for the forward motion of the car. Without friction the car would have stayed at the same place.
  • Brakes – Brakes are also an example where friction plays a vital role. Without brakes it would be nearly impossible to stop a car without damaging it. Brakes have saved a lot of lives and all the credits goes to presence of friction. Friction is the key take away in the entire car stopping process. It is due to the friction the car is stopped.
  • Stopping a ball – If we throw a ball and expect it to move only up to a certain distance, we will throw it with some amount of force. But what is the guarantee that the ball will not keep moving until eternity? It is the friction that takes place in between the ground surfrace and the ball because of which the ball is bound to stop. We always have a rough idea of amount of friction the surface will produce because of our experiences. So the ball stops at the desired location.
  • Spinning a cricket ball– A spinner rotates the ball while releasing it from his hand. The ball turs after touching the ground. This is because of the friction taking place between the pitch and the ball. The backward reaction force pushes the ball in the direction of spin thereby creating a turning effect.
  • Painting – While painting, the paint sticks to the surface of the paper. This is due to friction. The molecules of paint colours stick to the irregularities on the surface of the paper. This way the paint color does not fall off the paper even after drying. If we polish on a smooth surface, the paint might sometimes fall off because it does not create adhesive effect with the surface.
  • Drawing – Similar to painting, drawing also takes use of friction. It is very difficult to write on a smooth surface because of this reason. Mainly rough surfaces are the most suitable for writing but excessive roughness will create difficulty in writing hence an optimum roughness is required to write.
  • Cycling – Cycling takes use of friction to move forward, the reason being similar to that of walking, runing and driving a car. The tyres of cycle are subjected to forward push given by the normal reaction. This is possible with the help of friction. Without friction, the cycle wold not ave moved forward. It is important to observe that it is difficult to drive on a slippery road. Because slippery roads have very less friction.
  • Cleaning hands – While we clean hands we start rubbing our hands due to which the soap molecules comfortably sit inside the irregularities and take the dirt away from our hands. This is the reason why our hands are slippery when we apply soap. It is mainly due to the fact that soap molecules sit inside the irregularities and hence minimising the chances of friction.
  • Gears– The meshing of gear is an application of friction. As the teeth which are being meshed are simply the irregularities we talk about while discussing about friction, these gears stick to each other as a result of which motion transmission takes place.


Hi ....I am Abhishek Khambhata, have pursued B. Tech in Mechanical Engineering. Throughout four years of my engineering, I have designed and flown unmanned aerial vehicles. My forte is fluid mechanics and thermal engineering. My fourth-year project was based on the performance enhancement of unmanned aerial vehicles using solar technology. I would like to connect with like-minded people.

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