Practical Examples of Increasing and Decreasing Friction
A friction force prevents one object from rolling or sliding over another. Although frictional forces, like the traction required to walk without slipping, may be advantageous, they also pose significant resistance to motion. Automobile engines use about 20% of their output to overcome frictional forces in moving parts. The adhesion forces between the contact zones of the surfaces, which are always microscopically uneven, appear to be the primary cause of friction between metals.
Causes of Friction
The main source of friction is the irregularities on the surfaces in contact, which become interlocked when the surfaces come into contact.
Smooth surfaces have fewer irregularities, while rough surfaces have more irregularities. As a result, rough surfaces have a high friction coefficient.
The weight of the body also influences frictional force.
Types of Friction
Static friction- The frictional force between two surfaces while they are at rest in relation to one another, is known as static friction.
Dynamic friction- The force of friction that develops between any two surfaces when there is relative motion between them is known as dynamic friction.
How to Calculate the Friction Force Between Surfaces?
We have two types of friction, so we have two formulas to calculate the friction forces.
Static friction:
${{F}_{s}}$=${{μ}_{s}{F}_{N}}$
${{F}_{s}}$ = Maximum value of static friction force
${{μ}_{s}}$ = Coefficient of static friction
${{F}_{N}}$ = Normal reaction force
Dynamic friction:
${{F}_{k}}$=${{μ}_{k}{F}_{N}}$
${{F}_{k}}$ = Dynamic/Kinetic friction force
${{μ}_{k}}$ = Coefficient of kinetic friction
${{F}_{N}}$ = Normal reaction force
How is Friction Due to Air Reduced?
Friction is a force that resists object motion and can cause items to slow down. Friction is represented by air resistance. Moving objects are slowed by air resistance. The air resistance of an item is affected by physical features such as its form. Air friction is greatly decreased by streamlining the form of the body moving through air. Example: Jets, supercars and bullet trains have a streamlined design.
Ways for Decreasing Friction
Making use of lubricants: The application of lubricants like oil, grease, or graphite reduces the roughness of the surface. Lubricants minimise friction by filling the gaps of irregularities between surfaces in contact.
Polishing: Friction arises due to irregularities on the surface. On polishing, the irregularities decrease, and the surface offers less friction to a body moving over it.
Proper selection of material: Friction depends upon the nature of the material of surfaces in contact. Using materials with a low friction coefficient can reduce the friction force and improve efficiency. For example, rubber is used for making tires instead of iron.
Using ball bearings: converting sliding friction into rolling friction: we know that sliding a stone slab is difficult compared to rolling a wheel made of the same stone.
Streamlining: Air friction can be reduced significantly by streamlining the body's shape. For example, aircraft, missiles, and supercars have a streamlined shapes.
Ways for Reducing Friction
Why should friction be raised if it is the force that lowers productivity and damages equipment parts?
Some ways to increase friction-
Making the surface rough- cricketers use shoes with spikes to reduce slipping.
Making grooves on the surface - tires have grooves to offer high friction.
If we press the surfaces into each other more firmly, we can increase the friction between them.
Using dry and unlubricated parts.
Increase the area in contact with fluid: frictional force offered by fluids (liquids and gasses) is called frictional drag. It depends upon the area in contact with fluid; thus, by increasing the area in contact, we can increase friction.
Increasing Friction Examples
The tyres of motor cars and bicycles are rough to increase friction. when a ground or surface becomes slippery after rain or water splashing, it is made rough by spreading sand to increase the friction.
Decreasing Friction Examples
When objects are rolled over the surface, the friction between the rolled object and the surface can be reduced by using ball bearings. Using lubricants such as oil or grease can reduce surface friction. Polishing the surface makes the surface smooth, and friction can be reduced.
Summary
The friction force is a contact force whose magnitude depends directly upon the nature of surfaces in contact. Thus by altering the characteristics of surfaces, we can increase or decrease friction. By making the surface smooth, we can achieve reduced friction, while by making it rough, the magnitude of friction can be increased.
Solved problems
1. Amy is towing a 4 kg toy vehicle previously resting on the floor. Calculate the friction coefficient if the static frictional force is 50 N.
Solution:
Known:
m (Mass) = 4 kg,
${{F}_{s}}$ (static frictional force) = 50 N,
${{F}_{N}}$ (Normal force) = mg
= 4 Kg × 9.8 m/${{s}^{2}}$
${{F}_{N}}$= 39 N
${{μ}_{s}}$ = ${{F}_{s}}$ / ${{F}_{N}}$
${{μ}_{s}}$ = 50/39
${{μ}_{s}}$ = 1.282
2. Force of 60N is exerted on the box kept on the floor with a coefficient of static friction of 0.4. Find the friction force.
Solution:
The force of static friction is given by,
${{F}_{s}}$=${{μ}_{s}{F}_{N}}$
Here, ${{μ}_{s}}$ is the coefficient of static friction, and N is the normal force.
${{μ}_{s}}$= 0.4 and N=60N
Substituting the values in the equation,
${{F}_{s}}$=${{μ}_{s}{F}_{N}}$
${{F}_{s}}$=${{0.4}\times{60}}$
${{F}_{s}}$= 24 N
FAQs on How to Increase and Decrease Friction: Physics Made Simple
1. What does it mean to increase or decrease friction, and why are both actions important?
Increasing friction means making it harder for surfaces to slide past each other, while decreasing friction means making it easier. Both actions are crucial in different situations. We increase friction to get a better grip, like with car tyres on the road for safety. We decrease friction to make movement smoother and more efficient, like applying oil to machine parts to prevent them from wearing out.
2. What are some common methods used to increase friction in everyday life?
Friction is intentionally increased in many applications to improve safety and performance. The primary method is to make the surfaces in contact rougher. Key examples include:
- Treading Tyres: The grooves on car, bus, and bike tyres increase friction for better grip on the road, especially in wet conditions.
- Brake Pads: Brake systems in vehicles use pads made of high-friction material to press against the wheels and slow them down.
- Grooved Shoe Soles: Athletes and even daily footwear have grooved soles to prevent slipping and provide a firm grip on the ground.
- Kabaddi Players: They often rub their hands with soil to get a better grip on their opponents.
3. How can friction be reduced, and what are some practical examples?
Reducing friction is essential for efficiency and preventing wear and tear. Common methods to decrease friction include:
- Using Lubricants: Applying substances like oil or grease between moving parts (e.g., in a bicycle chain or engine) creates a thin layer that reduces direct contact and friction.
- Polishing Surfaces: Making surfaces smoother, like polishing a tabletop, reduces the interlocking of irregularities and thus lowers friction.
- Using Ball Bearings: These are used in fans, skateboards, and machines to replace sliding friction with much lower rolling friction.
- Streamlining: Designing objects with a special shape (e.g., aeroplanes, race cars) to reduce air or water resistance, which is a type of fluid friction called drag.
4. Why are the tyres of vehicles like cars and trucks treaded?
The tyres of vehicles are treaded to increase friction between the tyre and the road. These grooves, or treads, provide a better grip, which is crucial for controlling the vehicle, especially when braking or turning. In wet conditions, the treads also help to channel water away from the contact patch, preventing the vehicle from skidding on a layer of water and ensuring safety.
5. How is friction reduced for objects that move through air and water?
The frictional force exerted by fluids like air and water is called drag. To reduce drag, objects are given a special shape called a streamlined body. This shape, which is pointed at the front and tapered at the back, allows the fluid to flow smoothly around the object, minimising resistance. This is why aeroplanes, rockets, submarines, and even high-speed racing fish have streamlined bodies.
6. If friction causes wear and tear, why don't we try to eliminate it completely?
While friction does cause wear and wastes energy, it is also a necessary force for many essential activities. Without friction, we wouldn't be able to walk, as our feet would slip on the ground. Cars couldn't start or stop, and we couldn't hold a pen or light a matchstick. The goal is not to eliminate friction, but to manage it—increasing it where it's helpful and decreasing it where it's a hindrance.
7. Which is stronger: static, sliding, or rolling friction for the same two surfaces?
For the same pair of surfaces, the order of friction from strongest to weakest is: Static Friction > Sliding Friction > Rolling Friction. Static friction is the strongest because it's the force that must be overcome to start moving an object from rest. Sliding friction (also called kinetic friction) is weaker because less force is needed to keep an object moving. Rolling friction is the weakest, which is why it's easier to roll a heavy box on wheels than to drag it.
8. Is it possible to create a surface with absolutely zero friction?
No, in the real world, it is impossible to create a condition of absolutely zero friction. Every surface has some level of microscopic irregularities that cause friction when they come into contact with another surface. While we can significantly reduce friction by using lubricants, polishing, or magnetic levitation, we can never eliminate it completely. A zero-friction surface remains a theoretical concept used in physics problems.
