What is Friction Overview
When we toss a ball on the ground, it begins to move with some velocity. However, no force should be exerted in the direction of 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, implying that a force is operating on it. This force is referred to as "friction."
What is Friction?
Friction is described as the resistance provided by surfaces in contact as they move past each other. Friction is a force that prevents one thing from moving against another. The resistance to motion of one item moving relative to another is defined as "friction." According to the International Journal of Parallel, Emergent, and Distributed Systems, it is not considered a basic force like gravity or electromagnetics. Scientists believe it is caused by the electromagnetic attraction of charged particles on two surfaces that are in contact. There are as many exceptions to every basic rule concerning friction. According to the Royal Society, while two rough surfaces (such as sandpaper) rubbing against each other may have higher friction, very smoothly polished materials (such as plates of glass) that have been thoroughly cleansed of all surface particles may actually adhere to each other quite firmly.
Example of Friction
Consider a book on a table, it is now at rest. You give the book a nudge, and it begins to slide across the table. The novel eventually comes to an end. This is caused by frictional forces. The frictional force operates by exerting an equal force in the opposite direction of the moving item. As seen in the picture, the friction is traveling in the opposite direction of the push force. The friction will delay and, eventually, stop the book from sliding farther
How to calculate Friction Force?
Use the following formula to calculate the friction force-
F = μn |
Where,
F= Friction Force.
μ= Coefficient of Force.
n= Normal Force.
F = μmg |
Given that m is the object's mass and g is its acceleration due to gravity, the friction acts to resist the object's motion.
Factors affecting Friction
Friction is a force that is affected by outside causes. The two elements that influence friction are as follows-
Concerning the nature of the two surfaces in touch: Friction is determined by the smoothness or roughness of the two surfaces in contact with one another. The friction between the two is reduced when the surface is smooth since there is less interlocking of imperfections. Friction rises when the surface is rough.
Based on the force acting on these surfaces: When force is applied simultaneously with imperfections, friction rises.
Causes of Friction
Friction is created by imperfections on the two surfaces that come into contact. As a result, as one object travels over another, the surface imperfections become intertwined, causing friction. The more roughness, the more imperfections, and the greater the friction.
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Types of Friction
Friction is the force that prevents solid surfaces, fluid layers, and material components from sliding against each other. There are four forms of friction, which are as follows-
Dry Friction
Dry friction is the force that opposes the relative lateral motion of two in-touch solid surfaces. It is further classified as static friction ("stiction") between non-moving surfaces and kinetic friction ("stiction") between moving surfaces. Dry friction, with the exception of atomic or molecular friction, is caused by the interaction of surface characteristics known as asperities.
Example- The force resisting the sliding of a box on a surface and the frictional force at the tire-road contact region.
Fluid friction
It is the friction that occurs between moving layers of a viscous fluid.
Example- A person swimming in the water.
Internal friction
It is the force that resists motion between the components that make up a solid substance when it deforms.
Example- Two identical steel wires begin oscillating at the same moment.
Lubricated friction
It is a type of fluid friction in which two solid surfaces are separated by a lubricating fluid.
Skin friction
It is a component of drag, which is the force that resists fluid motion across the surface of a body.
Example- The flat plate or the pipe wall.
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Other Types of Friction
The following are some of the other types of friction-
Belt Abrasion
Belt friction is a physical phenomenon that is noticed when one end of a belt wrapped around a pulley is dragged. The belt friction equation may be used to model the resultant tension, which acts on both ends of the belt. In reality, the theoretical tension operating on the belt or rope as estimated by the belt friction equation may be compared to the maximum tension that the belt can withstand. This allows a rig designer to determine how many times the belt or rope must be wrapped around the pulley to keep it from slipping. When performing fundamental activities, mountain climbers and sailing crews display a common understanding of belt friction.
Braking Friction
Braking Friction Any wheel fitted with a brake is capable of producing a considerable retarding force, which is often used to slow and stop a vehicle or piece of spinning gear. Braking friction varies from rolling friction in that the coefficient of friction for rolling friction is modest, but the coefficient of friction for braking friction is intentionally big due to the materials used in brake pads.
Rolling Resistance
It is the force that prevents a wheel or other circular object from rolling over a surface due to deformations in the object or surface. In general, the force of rolling resistance is smaller than that of kinetic friction. The coefficient of rolling resistance is typically 0.001. The movement of motor vehicle tyres on a road is one of the most common instances of rolling resistance, a process that creates heat and sound as byproducts.
Triboelectric Effect
Rubbing different materials together can result in an electrostatic charge buildup, which can be dangerous if combustible gases or vapors are present. Explosions might result from the ignition of the combustible mixture when the static build-up discharges.
Applications of Friction
Friction is a significant aspect of many engineering fields. The following are some of the uses of friction-
Household Usage
Matchsticks are heated and ignited by friction (friction between the head of a matchstick and the rubbing surface of the matchbox). Sticky pads are used to keep objects from slipping off smooth surfaces by increasing the coefficient of friction between the surface and the item.
Measurements
A tribometer is a device that monitors surface friction. A profile graph is a device that measures the roughness of the pavement surface.
Transportation
- Automobile brakes rely on friction to slow a vehicle by turning its kinetic energy into heat. In fact, one of the technological challenges in building braking systems is safely dissipating this tremendous quantity of heat.
- Disk brakes rely on friction between a revolving disc and brake pads pushed transversely against it.
- Drum brakes generate friction by pressing brake shoes or pads against a revolving cylinder (the brake drum).
- Disc brakes offer higher stopping capability than drum brakes because they can be cooled more efficiently.
- Rail adhesion is the grip that a train's wheels have on the rails.
- The slipperiness of the road is an essential design and safety issue for automobiles.
- Split friction is a particularly hazardous phenomenon caused by variable friction on both sides of a vehicle. The interaction between tyres and the driving surface is influenced by road roughness.
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How to reduce Friction?
The following are some of the measures to reduce friction-
Devices
Wheels, ball bearings, roller bearings, and other forms of fluid bearings may convert sliding friction into a much smaller sort of rolling friction. In low-friction bearings, several thermoplastic materials, such as nylon, HDPE, and PTFE, are routinely employed. They are especially handy since the coefficient of friction decreases as the exerted weight increases. [69] For heavy loads or important bearings, very high molecular weights are typically required for enhanced wear resistance.
Lubricants
A lubricant, such as oil, water, or grease, is commonly used to minimize friction by being put between the two surfaces, frequently drastically lowering the coefficient of friction. Lubricant technology is the combination of lubricants with the application of science, particularly to industrial or commercial goals. Superlubricity, a newly found phenomenon, has been seen in graphite: it is the significant reduction in friction between two sliding objects, nearing zero values. Even so, a very minor amount of frictional energy would be wasted.
Others
Another method for reducing friction between two pieces is to provide micro-scale vibration to one of them. This can be sinusoidal vibration, as in ultrasound-assisted cutting, or vibration noise referred to as "dither."
Laws of Frictions
The following are 5 laws of friction-
- The friction between a moving object and a normal force is proportional and perpendicular.
- The coefficient of static friction is greater than the coefficient of kinetic friction.
- Kinetic friction is unaffected by velocity.
- Friction occurs independently of the area of contact for as long as one exists.
- The sort of surface with which the object comes into contact determines its friction.
Sample Solved Questions of Friction
Sample Question 1: Using brakes in an automobile slows the motion, despite the fact that it is an internal force. Why?
Ans. The use of brakes constitutes external forces for the automobile's system, brakes, and the road on which it is going, and therefore the car retards. The friction acts against the movement of the automobile.
Sample Question 2: What causes friction to be a non-conservative force?
Ans. Because the amount of work done by friction depends on the route, it is a non-conservative force.
Sample Question 3: A girl drives her toy car through a dry marble floor, a wet marble floor, newspaper, and a towel on the floor. Arrange the friction force operating on the automobile on various surfaces in increasing order.
Ans. The nature of two surfaces determines their friction force. Friction increases as the surfaces in contact get rougher. The wet marble floor will be subjected to the least amount of force since it is the least abrasive of the three. So, in order of roughness, the roughest are wet marble floor, dry marble floor, newspaper, and towel. As a result, the force will follow the same pattern.
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Fun Facts about Friction
- Wheels, while excellent for rolling and minimizing friction, could not function without friction. The more tightly two surfaces are forced together, the more effort is required to overcome friction and allow them to glide.
- Standing up without friction would be quite difficult.
- Fluid friction is commonly employed in water parks to allow us to glide down huge slides smoothly and quickly.
- Static electricity may be generated via friction.