Frictional force is a force that resists motion between two surfaces in contact. It acts in the opposite direction to the applied force and can cause objects to slow down or stop moving. The strength of frictional force depends on the nature of the surfaces in contact, the force pushing the surfaces together, and the roughness of the surfaces. In everyday life, frictional force is encountered in activities such as walking, driving, and using tools.
Table of Contents
Type of Frictional Force
| Type of Frictional Force | Formula | Variables | Description | Examples |
| Static frictional force | Fs ≤ μs N | Fs = force of static friction μs = coefficient of static friction N = normal force | Force that opposes motion when two surfaces are not moving relative to each other | Pushing a heavy box on the floor, a car’s tires gripping the road surface before it starts to move |
| Kinetic frictional force | Fk = μk N | Fk = force of kinetic friction μk = coefficient of kinetic friction N = normal force | Force that opposes motion when two surfaces are moving relative to each other | Sliding a book across a table, a sled sliding down a snowy hill |
| Rolling frictional force | Fr = μr N | Fr = force of rolling friction μr = coefficient of rolling friction N = normal force | Force that opposes motion when a round object, such as a wheel or ball, rolls on a surface | A car’s wheels rolling on the road, a bowling ball rolling on a lane |
Note that in all the formulas, N represents the normal force acting between the two surfaces, and the coefficients of friction (μ) are dimensionless constants that depend on the materials and surfaces in contact. The examples illustrate some common situations where frictional force is encountered in everyday life.
Daily Life Examples of Frictional Force
- Walking – Friction between your shoes and the ground helps you to walk and maintain your balance.
- Writing – Friction between the pen or pencil and paper helps you to write and make marks on the paper.
- Brakes on a car or bicycle – Frictional force between the brake pads and the wheel slows down or stops the vehicle.
- Cooking – Friction between the pan and the stove helps to cook food evenly.
- Zippers and Velcro – Frictional force helps to keep zippers and Velcro fastened.
- Cleaning – Frictional force is what allows a mop or a broom to pick up dirt and debris off the floor.
- Climbing – Friction between your hands or feet and the surface of a rock or wall helps you to climb.
- Playing sports – Frictional force is present in many sports, such as basketball, where the friction between the ball and the court affects the trajectory of the ball.
Advantages and Disadvantages of Frictional Force
| Advantages | Disadvantages |
| Helps us to walk and maintain our balance. | Creates wear and tear on surfaces, causing them to deteriorate over time. |
| Enables us to write, draw, and make marks on paper. | Can cause damage to machinery and equipment through frictional heating and wear. |
| Allows us to stop or slow down vehicles, preventing accidents. | Can create unwanted noise through vibration and friction. |
| Helps us to cook food evenly and safely. | Can cause discomfort or injury if excessive friction is applied to skin or body parts. |
| Helps to keep clothing fastened and secure. | Can reduce efficiency in mechanical systems by increasing energy loss due to frictional resistance. |
| Enables cleaning by allowing mops and brooms to pick up dirt and debris. | Increases energy consumption – Frictional force can increase energy consumption in many mechanical systems, such as engines and turbines, leading to higher energy costs and decreased efficiency. |
Summary
- Frictional force opposes motion between two surfaces that are in contact with each other.
- The amount of frictional force depends on the nature of the surfaces, force pressing them together, and the speed of motion.
- Frictional force can be static or kinetic.
- Coefficient of friction is a measure of frictional force and can be determined experimentally.
- Frictional force is beneficial in many situations, such as walking, writing, and physical activities.
- Frictional force can reduce the efficiency of mechanical systems and can be reduced by lubrication or smoothing surfaces.
- Lubricants reduce frictional force by creating a layer between surfaces.
- Rolling friction is different from other types of frictional force and is typically lower in magnitude.
- Surface roughness affects frictional force.
- Frictional force prevents slipping and sliding in various situations.
More Interesting Links
Fluid Friction| Definition, Types, and Factors Affecting
Reynold’s Number Formula| Daily Life Examples
Dynamic Viscosity-Formula Derivation
Inertia and the Laws of Motion
Exams Related Questions
| No. | Question | Answer |
| 1. | What is frictional force and how does it arise between two surfaces? | Frictional force is a force that opposes motion between two surfaces that are in contact with each other. It arises due to the microscopic irregularities on the surfaces of objects that come into contact with each other. |
| 2. | What are the factors that affect the amount of frictional force between two surfaces? | The amount of frictional force between two surfaces depends on several factors, including the nature of the surfaces in contact, the force pressing them together, and the speed of motion. |
| 3. | Describe the differences between static and kinetic frictional force. | Static frictional force is the force that opposes the motion of an object that is at rest. Kinetic frictional force is the force that opposes the motion of an object that is already in motion. |
| 4. | How can the coefficient of friction be determined experimentally and what is its significance? | The coefficient of friction can be determined experimentally by measuring the force required to move an object across a surface and dividing it by the force pressing the object and surface together. It is a measure of the frictional force between two surfaces and is dependent on the nature of the surfaces in contact. |
| 5. | What are some common examples of situations where frictional force plays a beneficial role? | Frictional force plays a beneficial role in many situations, such as allowing us to walk, write, and perform physical activities. It also helps to stop or slow down vehicles, enables cooking, cleaning, and allows sports players to grip equipment and surfaces. |
| 6. | Describe the effect of frictional force on the efficiency of mechanical systems and how it can be reduced. | Frictional force can reduce the efficiency of mechanical systems by increasing energy loss due to frictional resistance. It can be reduced through the use of lubricants or by smoothing the surfaces in contact. |
| 7. | Explain how lubricants work to reduce frictional force and give examples of common lubricants used in everyday life. | Lubricants work by creating a layer between two surfaces that reduces the frictional force between them. Common lubricants used in everyday life include oils, greases, and graphite. |
| 8. | What is rolling friction and how is it different from other types of frictional force? | Rolling friction is the frictional force that opposes the motion of an object that is rolling over a surface. It is different from other types of frictional force, such as static or kinetic friction, because it is typically much lower in magnitude. |
| 9. | How does the type of surface affect the frictional force between two objects? | The type of surface in contact affects the frictional force between two objects. Rough surfaces create more frictional force than smooth surfaces. |
| 10. | Describe the role of frictional force in preventing slipping and sliding in various situations, such as walking or driving. | Frictional force plays a crucial role in preventing slipping and sliding in various situations. It allows us to maintain our balance while walking and prevents vehicles from sliding on the ro |
Related Links
Tension Formula| Daily Life Examples
Kinetic Energy Formula-0.5mv^2
Definition of Work in Physics| Work Formula
Critical Velocity of Fluids| Daily Life Examples
PhD Student at University College Dublin and Author at What's Insight
PhD Student who loves to write about science, technology and more. Studying at the University College in Dublin. Hope you enjoy my content.
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