Content

• To step
• Method 1 of 2: Creating a rougher surface
• Method 2 of 2: Increase the resistance in a liquid or gas
• Warnings

Have you ever wondered why your hands get warm when you rub them together quickly or why you can actually start a fire by rubbing two sticks together? The answer is friction! When two surfaces rub against each other, they will oppose each other's movement at a microscopic level. This resistance will generate energy in the form of heat, which you can use to warm your hands, make a fire, etc. The greater the friction, the more energy will be released, so know how to increase the friction between two moving ones. parts in a mechanical system basically give you the opportunity to generate a lot of heat!

To step

Method 1 of 2: Creating a rougher surface

1. Create more “rough” or sticky contact points. When two materials slide or rub against each other, three things can happen: small corners, cracks and irregularities on the surface can get caught; one or both surfaces can deform in response to the movement; and, eventually, the atoms in any surface can begin to interact. For practical purposes, all three of these do the same thing: create friction. Choosing surfaces that are abrasive (like sandpaper), deform (like rubber), or tacky (like glue, etc.) is an easy way to increase friction.
   • Technical textbooks and similar resources can be great aids in selecting materials to use for increasing friction. Most standard building materials have a known "coefficient of friction" - that is, a measure of how much friction is generated along with other surfaces. The coefficients of friction for only a few known materials are listed below (a higher value indicates a higher friction):
   • Aluminum on aluminum: 0.34
   • Wood on wood: 0.129
   • Dry concrete on rubber: 0.6-0.85
   • Wet concrete on rubber: 0.45-0.75
   • Ice on ice: 0.01
2. Push the two surfaces together harder. A basic definition in physics states that the friction an object undergoes is proportional to the normal force (for our purpose this force is equal to that with which the object pushes against the other). This means that the friction between two surfaces can be increased if the surfaces are pushed together with more force.
   • If you've ever used brake discs (for example, those on a car or bicycle) you've seen this principle in action. In this case, by pressing the brakes, a set of friction-generating blocks are pushed against metal discs that are attached to the wheels. The harder you press the brakes, the harder the blocks will be pressed against the discs and there will be more friction. This allows you to stop the vehicle quickly, but also releases a lot of heat, which is why braking systems are often very hot after heavy braking.
3. Stop any relative movement. This means that if one surface moves relative to another, you stop it. So far we have focused on dynamic (or "sliding") friction - the friction that occurs when two objects or surfaces rub against each other. In fact, this form of friction is different from static friction - the friction that occurs when an object starts to move against another object. In essence, the friction between two objects is greatest when they start to move against each other. Once they are in motion, the friction decreases. This is one of the reasons why it is difficult to get a heavy object moving than to keep it.
   • To observe the difference between static and dynamic friction, try the following simple experiment: Place a chair or other piece of furniture on a smooth floor in your home (not on a rug or carpet). Make sure the furniture does not have any protective "studs" on the bottom or any other type of material that will make it easier to slide on the floor. Try the furniture just push hard enough so it starts moving. You should notice that once the furniture starts to move, it immediately becomes much easier to push. This is because the dynamic friction between furniture and floor is smaller than the static friction.
4. Remove liquids from between surfaces. Liquids such as oil, grease, petroleum jelly, etc., can significantly reduce friction between objects and surfaces. This is because the friction between two solids is usually much higher than that between solids and a liquid in between. To increase friction, you can take all possible liquids out of the equation, with only "dry" parts causing friction.
   • To get an idea of ​​how much liquids can reduce friction, try the following simple experiment: Rub your hands together if they are cold and you want to warm them up. You should be able to immediately notice that they are getting warmer from the rubbing. Then put a fair amount of lotion on your palms and try to do the same again. Not only should it be easier to rub your hands together quickly, but you will also notice that they get less hot.
5. Remove wheels or carriers to create sliding friction. Wheels, carriers and other "rolling" objects experience a special type of friction called rolling friction. This friction is almost always less than the friction generated by sliding the same object over the ground. - This is why these objects tend to roll and not slide on the ground. To increase the friction in a mechanical system, you can remove the wheels, carriers, etc., so that the parts slide against each other, not roll.
   • Consider, for example, the difference between pulling a heavy weight over the ground in a carriage versus an equivalent weight in a carriage. A wagon has wheels, so it is easier to pull than a sledge, which drags along the ground while generating a lot of sliding friction.
6. Increase the viscosity. Solid objects aren't the only things that can create friction. Liquid substances (liquids and gases such as water and air, respectively) can also create friction. The amount of friction that a liquid generates when it flows past a solid depends on several factors. One of the easiest to control is viscosity - that's what is commonly referred to as "thickness". In general, liquids with a high viscosity (those are "thick", "sticky", etc.) will cause more friction than liquids that are less viscous (those are "smooth" and "liquid").
   • For example, consider the difference in effort you will have to make when you blow water through a straw versus blowing honey through a straw. Water is not very viscous and will move easily through the straw. Honey is much more difficult to blow through a straw. This is because the high viscosity of the honey generates a lot of resistance and thus friction when it is blown through a narrow tube such as a straw.

Method 2 of 2: Increase the resistance in a liquid or gas

1. Increase the viscosity of the liquid. The medium through which an object moves exerts a force on the object which, as a whole, tries to cancel the frictional force on the object. The denser a liquid is (and therefore more viscous), the slower an object will move through that liquid under the influence of a given force. For example: a marble will fall through air much faster than through water, and through water faster than through syrup.
   • Viscosity of most liquids can be increased by lowering the temperature. For example: a marble falls slower through cold syrup than through syrup at room temperature.
2. Increase the area exposed to air. As indicated above, liquid substances such as water and air can generate friction when they flow past solids. The frictional force experienced by an object while moving through a liquid substance is called resistance (depending on the medium, this is also called "air resistance", "water resistance", etc.). One of the properties of resistance is that an object with a larger cross-section- that is, an object with a greater profile as it moves through the fluid - experiences more resistance. This gives the liquid more surface to push against, which increases the friction on the object as it moves through it.
   • Suppose a pebble and a sheet of paper each weigh one gram. If we let both fall at the same time, the pebble will fall straight down while the sheet of paper will slowly swirl down. This is where you see the air resistance in action - the air pushes against the large, wide surface of the paper creating resistance and the paper falling down much more slowly than the pebble, which has a relatively narrow cross-section.
3. Choose a shape with greater resistance. Although the cross-section of an object is a good one general is an indication of the size of the resistor, in reality resistor calculations are a lot more complicated. Different shapes behave in different ways in the liquids they pass through - this means that some shapes (eg flat plates) are more resistant than others (eg spheres) made of the same material. Because the measure of the relative magnitude of the air resistance is also called the "drag coefficient", it is said that shapes with a large air resistance have a higher drag coefficient.
   • Consider, for example, the wings of an airplane. The shape of a typical wing of an airplane is called a airfoil. This smooth, narrow and rounded shape moves easily through air. The drag coefficient is very low - 0.45. On the other hand, you can imagine that a wing has sharp angles, is block-shaped or looks like a prism. These wings generate a lot more friction because they generate a lot of resistance in flight. Prisms thus have a greater drag coefficient than wing profiles - about 1.14.
4. Make the object less streamlined. Another phenomenon related to the different drag coefficients of the various shapes is that objects with a larger, more square-shaped "streamline" generally generate more drag than other objects. These objects consist of rough, straight lines and usually do not narrow towards the back. On the other hand, streamlined objects are often more rounded and taper towards the back - like the body of a fish.
   • For example, the way the average family car is designed today compared to the same type decades ago. In the past, cars were much more blocky and had much more straight and rectangular lines. Today, most family cars are much more streamlined and, to a large extent, softly rounded. This is done on purpose - a streamlined shape means that a car experiences less drag, reducing the effort of the engine to move the car (and reducing gas mileage).
5. Use material that allows less air to pass through. Some materials allow liquids and gases to pass through. In other words, there are holes for the liquid to pass through. This ensures that the surface of the object against which the liquid is pushing becomes smaller, so there is less resistance.This property remains valid even if the holes are microscopic - as long as the holes are large enough to allow liquid / air to pass through, the resistance will be reduced. This is why parachutes, designed to generate a lot of air resistance and thereby reduce the speed of falling of someone or something, are made of strong, light silk or nylon and not cotton or coffee filters.
   • To give an example of this property in action, think about what happens to a ping-pong bat when you drill a few holes in it. It then becomes much easier to move the paddle quickly. The holes allow air to pass through while swinging the paddle, which greatly reduces resistance and allows the paddle to move faster.
6. Increase the speed of the object. Finally, regardless of the shape of an object or how permeable the material it is made of, the resistance it encounters will always increase as it moves faster. The faster an object moves, the more liquid it will have to move, which in turn increases the resistance. Objects moving at very high speeds can experience very high friction due to the high resistance, so these objects will usually be streamlined there or else they will fall apart due to the force of the resistance.
   • Consider the Lockheed SR-71 "Blackbird", an experimental spy plane built during the Cold War. The Blackbird, which could fly at speeds greater than mach 3.2, encountered extreme resistance from those high speeds, despite its streamlined design - extreme enough to cause the aircraft's metal fuselage to expand due to the heat generated by friction from the air during flight. fly.

Warnings

• Extremely high friction can release a lot of energy in the form of heat! For example, you really don't want to touch the brake pads of your car right after you hit the brakes hard!
• The great forces released when dragged through a fluid can cause structural damage to that object. For example, if you stick the flat side of a thin piece of plywood into the water while driving a speedboat, there is a good chance that it will be torn to shreds.