CBSE class 11 Physics Note: Laws of Rolling Friction Explained

Have you noticed the ball begins to move quickly when you throw it on the ground? However, no force should be exerted in the direction of the applied motion, and the ball should continue to roll according to Newton’s first law, but this does not occur. Instead, the ball comes to a halt after a set distance, indicating that a force is acting on it. This force is referred to as “friction”.

One can refer to friction as a force opposite of the force that one applies. It means that when an object moves along a surface, it gradually stops. The object stops because of the force of friction that acts instead of the force applied.

No matter what direction the force is, the force of friction will always act as opposed to it. It is interesting to know that the force of friction has applications in various physics concepts. One can benefit in competitive exams like NEET or JEE by having a thorough understanding of- friction and the various types of frictions.

What do you understand about friction?

Friction is a force defined as the resistance provided by surfaces in touch as they move past one another. For example, When a person throws a ball on a flat surface, the ball eventually comes to rest after some time. It happens because of friction acting between the surface and the ball.

Friction offers the necessary traction for walking without slipping. In most circumstances, friction is beneficial. They do, however, provide a significant level of opposition towards the move. Furthermore, around 20% of an automobile’s engine power is used to overcome frictional forces in the mechanical parts. Let us look at some of these aspects in the next section.

What are the factors that affect friction?

Friction is defined as a force that is influenced by outside forces. Note that two elements influence the force of friction:

1. Concerning the characteristics of the two surfaces in touch

The softness or roughness of two surfaces in touch determines friction. Because there is less interlocking of imperfections when the area is smooth, friction between the two is reduced. Friction increases when the surface is rough.

2. On the force exerted on these surfaces

When a force is applied alongside imperfections, friction increases, which means that in case of irregularities, the force of friction acting on the surface increases.

What causes friction?

The abnormalities on the two surfaces in contact can generate friction. As a result, when one object passes over another, the imperfections on the surface become intertwined, causing friction. The rougher the surface, the more imperfections, and friction will be greater.

What are the different types of friction?

Fiction happens when opposing forces start acting between the two bodies in motion. However, four types of friction are classified based on different characteristics. They are-

• Sliding friction
• Fluid friction
• Static friction
• Rolling friction

Explain the different types of fiction

• Sliding friction

Sliding or kinetic friction is the frictional force that prevents genuine relative sliding motion from acting between two surfaces in contact. If there is a heavy object on a ground surface, a weak force would not be enough to move the metal block.

The metal block begins to move as you gradually increase the force until it reaches a certain point. The resistive force offered by the heavy object in its static form is the same as the governing strength of the force at which the heavy object begins to move. Static friction is the name given to this resistant force.

Continuing the experiment and increasing the force causes the metal block to move. However, even after the heavy object has begun to move, it continues to exert a resistant force in an attempt to stop it. It is referred to as ‘sliding friction.’ The sliding friction is lesser than the static friction, based on what has been experimented with.

• Fluid friction

Fluid friction occurs when two fluid layers move in opposite directions. Viscosity, often known as viscous drag or fluid friction, is the internal resistance to flow.

The viscosity of a fluid is commonly referred to as the fluid’s “thickness.”

Water is “thin,” meaning it has a lower viscosity, but honey is “thick,” meaning it has a higher viscosity. The less-dense fluid is, the easier it is to distort or move it.

All actual fluids (excluding superfluids) are vicious because they resist shearing in a way.

• Static friction

It is observed that moving a rolling cart is more difficult than keeping it moving? The first effort is the most difficult when attempting to move your sofa across the space. People may think it is all in their heads, but there is a physical basis.

Static friction is the cause. Friction is a force that makes it more difficult for two items to slide alongside one another. The force of friction between a stationary body and the surface on which it is resting is known as static friction.

• Rolling friction

Each object receives a contact force; whenever the surface of one object slides over the surface of another. This contact force, which always opposes relative motion between the two surfaces, is called frictional force. The frictional force is applied tangentially to the two-body interface.

Rolling Friction or Rolling Resistance is the force that opposes the motion of a rolling body on a surface. A wheel or a ball rolling on the ground experiences this form of friction. Rolling friction is the force of friction between two surfaces when one is rolling over the other. Kinetic friction is analogous to rolling friction.

What is rolling friction?

The type of friction encountered by an object when in a rolling motion on some other surface is known as rolling friction, rolling resistance, or rolling drag. Rolling friction is frequently significantly lower in magnitude than sliding friction, which occurs when one surface of a body is in contact with the surface all through the motion.

There are two primary types of frictional forces that act on a moving solid body:

• Rolling friction or rolling resistance is the force that opposes the motion of a rolling object on a surface. It can be demonstrated by a ball or wheel rolling on the ground.
• Sliding friction is the other form of frictional force. Because only one part of the object is in contact with the surface in this sort of friction, the body’s movement is restricted. Sliding friction is demonstrated by pushing a box over a table.
• Sliding friction is much stronger than rolling friction.

What are the laws of rolling friction?

It is understood that rolling friction is a kind of friction that acts between the surfaces of the two rolling bodies. Three laws explain this concept.

Three laws govern the Rolling friction:

• The force of rolling friction reduces as the smoothness of the surface increases.
• Rolling friction is calculated as a load function and a fractional power constant.
• The radius of curvature is inversely proportional to the rolling friction force, which is directly proportional to the load.

What are the causes of rolling friction?

Certain things happen when a body is rolled on a flat surface:

1. At the place of contact with the surface, the object deforms.
2. The surface is distorted at the place of contact with a surface.
3. As a result of the points above, motion is formed beneath the surface.

The deformation energy is more than the energy of recovery, which is the fundamental cause of friction. In addition, there is an adhesive force between both two surfaces that must be overcome regularly. Several factors in determining the degree of friction include:  

• The sliding body’s quality
• The surface’s condition
• Load
• The rolling object’s diameter
• The body’s total surface area

What do you understand about the coefficient of rolling friction?

The coefficient of rolling friction μR = F/G, where F is the force required to move the axle of a tyre horizontally in the direction of motion, and G is the vertical load on the tyre, assuming it is rolling on a level horizontal surface.

State some examples of rolling friction

Some daily life examples that clearly show the phenomena of rolling friction are –

• A football rolling on the field will eventually rest because of the rolling friction acting on it.
• Motorbikes with broader wheels will burn more fuel as the chances of rolling friction are increased.
• A spherical body rolled on a surface with grass will only cover a little distance compared to a spherical body rolled on a smooth surface.

Conclusion

The concept of friction comes into play during various instances. For example, when matchsticks are lit, friction comes into play. The frictional force is created by the movement of pistons in a cylinder. Because there is friction between the pen and the board, writing on books and boards is feasible. Apart from this, the above details regarding the laws of rolling friction help a person understand its significance and applications.

FAQs

1. What are the causes of friction?

The abnormalities on the two surfaces in contact can generate friction. As a result, when one object passes over another, the imperfections on the surface become intertwined, causing friction. The rougher the surface, the more imperfections, and friction will be greater.

2. What are the factors responsible for rolling friction?

Several factors, including: determining the degree of friction

• The sliding body’s quality.
• The surface’s condition
• Load
• The rolling object’s diameter
• The body’s total surface area

3. What is the difference between sliding friction and rolling friction?

Sliding or kinetic friction is the frictional force that prevents genuine relative sliding motion from acting between two surfaces in contact. If there is a heavy object on a ground surface, a weak force would not be enough to move the metal block. At the same time, rolling friction or rolling resistance is the force that opposes the motion of a rolling body on a surface. A wheel or a ball rolling on the ground experiences this form of friction. Rolling friction is the force of friction between two surfaces when one is rolling over the other.

4. What are the daily life examples of rolling friction?

Some daily life examples that clearly show the phenomena of rolling friction are –

• A football rolling on the field will eventually rest because of the rolling friction acting on it.
• Motorbikes with broader wheels will burn more fuel as the chances of rolling friction are increased.
• A spherical body rolled on a surface with grass will only cover a little distance compared to a spherical body rolled on a smooth surface.

5. What are the three laws of rolling friction?

Three laws govern the Rolling friction:

• The force of rolling friction reduces as the smoothness of the surface increases.
• Rolling friction is calculated as a load function and a fractional power constant.
• The radius of curvature is inversely proportional to the rolling friction force, which is directly proportional to the load.