Frictional Force - Definition, Types, Examples, and FAQs

Frictional Force - Definition, Types, Examples, and FAQs

Friction is the force that prevents motion when the surface of one object comes into contact with the surface of another. The machine's mechanical advantage is reduced by friction, or in different words, the ratio of output to input is reduced due to friction. A car uses a quarter of its energy to reduce friction.

Yet it is also the friction in the tires that allows the vehicle to stay on the road and the friction in the clutch that allows it to drive. From matches to machines to molecular structures, friction is one of the most significant phenomena in the physical world. In this article, we will discuss frictional force and its different types.

Also, Read -10 disadvantages of friction

Table of Content ● ● ● ● ●

Definition Calculating the Force of Friction Types of Frictional Force Solved Examples Frequently Asked Question (FAQs)

Definition Frictional force refers to the force that resists the sliding or rolling of one solid object over another.

Calculating the Force of Friction The maximum amount of friction force that the surface can apply upon an object can be calculated with the given formula: Ffrict = µ • Fnorm To calculate the frictional force we have provided the basic steps to follow while calculating the friction force. ● Find the Normal Force It refers to the support force exerted upon an object in contact with a different stable object. The normal force can be calculated in most cases by the following formula:

N = mg In this formula, m indicates the object's mass, and g stands for the acceleration due to gravity. In the inclined surface case, the strength of the normal surface is reduced the more the surface is inclined, hence the formula becomes: N = mg cos(θ) θ represents the angle to which the surface is inclined. In a simple calculation, you have to find the normal force of a 3-kg block of wood sitting on a surface as N = 3 kg × 9.8 N/kg = 29.4 N ● Finding the Right Co-efficient The coefficient you would choose depends on the object and the specific situation. If the object is not moving on the surface, you use the coefficient of static friction. μ static, but if the object in question is moving, you use the coefficient of sliding friction μ slide. The coefficient also affects the type of materials used. For example, if the block were on a brick surface, the coefficient would be 0.6, but if it were on a pure wood block, it would range from 0.25 to 0.5. ● Calculating Frictional Force As mentioned, the formula for the frictional force is given by F = μN. As an example, consider a block of wood weighing 3 kg lying on a table to be moved from rest. In this case, we consider the coefficient of static friction. 0.5 is the static coefficient of wood.

With the details given, we can calculate the normal force as N = 3 kg × 9.8 N/kg = 29.4 N Now that we have the values ​of the normal force and the static coefficient of friction, we can calculate the friction force as follows: F = 0.5 x 29.4 N = 14.7 N

Types of Frictional Force

Friction is the force that compares with motion between surfaces touching the base.

Static, kinetic, sliding, and rolling friction occur between solid surfaces. Fluid friction occurs in both liquids and gases. All four types of friction are described below: ● Dry Friction ● Fluid Friction

Dry Friction Dry friction describes the reaction between the two solid bodies in contact when they are in motion (kinetic friction) and when they are not in motion (static friction). Both static and kinetic friction is proportional to the normal force between solid bodies. The interaction of various substances is modeled with different coefficients of friction. We also mean that certain substances have a higher resistance to motion than others, given the same normal force. Each of these values ​is determined experimentally.

1. Static friction Static friction occurs before the box slides and moves. In this region, the frictional force will be equal in scale and in the opposite direction to the pushing force itself. As the degree of pushing force increases, so does the frictional force. If only the magnitude of the pushing force continues to increase, the box will eventually begin to slide once the case begins to slide. The type of friction that prevents the case from moving changes from static friction to what is known as kinetic friction.

The point just before the box slides is called the impending motion. This can also be assumed as a maximum static frictional force before slipping. The sum of the max. static frictional force equals the static coefficient of friction times the normal force existing between the box and the surface. The coefficient of friction is a property that usually depends on both materials and can generally be looked up in tables.

2. Kinetic Friction Kinetic friction generally occurs beyond the point of coming motion as the box slides.

With the kinetic friction, the magnitude of the frictional force opposing the motion will equal the kinetic coefficient times the normal force of friction between both the box and the surface. The kinetic coefficient of friction also rests on two things in contact, but it will be almost less than the static coefficient of friction.

3. Rolling Friction Rolling friction occurs when a wheel, ball, or cylinder rolls freely over a surface, as in ball and roller bearings. The main cause of rolling friction appears to be the energy distribution involved in twisting objects. If a hard ball is rolled on a flat surface, the ball is somewhat compressed, and the flat surface is somewhat dented in the contact areas.

The elastic band or compression created at the front of the part in contact interferes with movement that is not fully compensated for as the fabrics spring back to the typical shape at the back. The internal losses in these two substances parallel those that prevent the ball from bouncing back to the level from where it is released. Coefficients of sliding friction are typically 100 to 1000 times larger than the coefficients of rolling friction for the corresponding materials.

4. Sliding friction

Sliding friction is the friction that acts on objects as they slide over a surface. Sliding friction is weaker than static friction. This is why it is easier to move a piece of equipment across the floor after you start moving than to set it in motion. Sliding friction can be valuable. For example, when writing with a pen, you use sliding friction. The "tip of the pen" slides easily across the paper, but there is enough friction between the pen and the paper to leave a mark.

Fluid Friction Fluid friction occurs between layers of fluid moving against each other. This internal flow conflict is called viscosity. In everyday terms, the viscosity of a liquid is referred to as its "thickness". All actual fluids have some resistance to shear and are therefore vicious. It is very useful to use the concept of an ideal fluid that does not resist shear and is not as vicious.

Solved Examples Q1. A huge block of ice is being pulled across a lake of frozen. The ice block has a mass of 200 kg. The coefficient of friction between the two ice surfaces is small: μk = 0.04. Calculate the force of friction that is acting on the block of ice.

Ans. On a flat surface, the normal force on an object is given by N = mg.

By using this, we can calculate the force of friction: Ff =μmg Substituting the given values in the above equation, we get, Ff =0.04 × 200 kg × 9.8 m/s2 = 78.4 kg-m/s2 or 147 N. Q2. A boy must push his boat across the mud to get to the water on the shore.

The coefficient of friction between both the boat and mud is given by μ = 0.600. If the boat has a mass of 60 kg, calculate the magnitude of the force of friction acting on the boat.

Ans. On a flat surface, the normal force on an object is N = mg.

Using this, we can find the force of friction: F = μN

F = μ mg Substituting the given values in the equation, we get F = (0.600)(60.0 kg)(9.80 m/s2) F = 352.8N

Frequently Asked Question (FAQs) Q1. Write the formula to calculate the frictional force.

Ans. F = μN Q2. What will happen if there is no frictional force?

Ans. Friction prevents the objects from sliding apart. Everything will move to the lowest point if there were no friction. It will be impossible to scale anything.

Q3. What increases friction?

Ans. It can be increased by making the surfaces rough and pressing them harder against each other (by increasing normal force).

Q4. Does friction depend on the area?

Ans. Friction is dependent on the shape and area of the surface in contact.

Q5. Which friction is greatest?

Ans. Static friction Q6. Does water increase friction?

Ans. Compared to dry friction, the presence of small amounts of water or humid air in the sliding interface can lead to an increase in friction force.

Q7. Explain the laws of friction for two bodies in contact with each other ?

If the two bodies in contact with each other are slipping over each other or having relative motion with respect to each other, the friction that is involved is kinetic friction and is given by: Read more

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