#### • Class 11 Physics Demo

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#### • air friction

Friction is the force that resists the relative motion of solid surfaces, fluid layers and elements that slide against each other. Friction is of several types fluid friction, lubricated friction, internal friction, skin friction,  dry friction and sliding friction.

• Dry fiction is the relative resistance in the lateral motion of two solid surfaces which are in contact.
• Fluid friction is described as the friction between the layers of viscous fluid.
• Lubricated friction is the fluid friction where a lubricating fluid separates two solid surfaces.
• Internal friction is the force that resists the motion between the elements that make up a solid material while it undergoes distortion.
• Skin friction is the force the resists the motion of a fluid across a body surface.
• Friction produces heat in various parts of machines, this one of the main disadvantage of friction. In this way some of the useful energy is wasted as heat energy.
• More power has to be exerted on machines due to friction.
• Friction opposes motion.
• Noise is also produced in machines due to friction.
• Engines of automobiles consume more fuel due to friction.
• Efficiency of machine is decreased; energy is lost due to heat.
• Friction counteracts movements and so it takes more energy to move. It causes unwanted heat.
• Rubber shoes or soles are worn out due to friction.
• Friction between trees causes forest fires.
• Friction slows down or stops the movement of objects. For example: A bicycle will stop eventually if it is not cycled consistently and continuously. If the bicycle has to be sped up, it has to be cycled faster. Hence, it more energy is needed to overcome the frictional force.
• Friction causes the surface of an object to wear out. For example: Soles of shoes and surface of tyres are worn out due to friction.
• Friction produces unnecessary heat. For example: Engines of cars becomes hotter due to friction.

#### Best Results From Yahoo Answers

Answers:So imagine if everything were completely slippery. That would be good for some machines that require parts to slide over one another. That would be bad for most things in real life. Like walking or driving or holding things.

Question:

Answers:Advantage first - without friction, life as we know it cannot continue! We cannot walk on a road or in the house. We can't use our normal modes of transport. Try living like in a space ship! Disadvantages - friction needs extra force to be overcome and thus consumes energy. Friction leads to wear and tear of surfaces.

Question:

Answers:Depends on what these forces are used for doesn't it? For example, if I'm trying to lean a ladder up against a wall, the advantage of friction is that the ladder will not slide away from the wall. The disadvantage of gravity is that it's trying to slide the ladder down and away from the wall. On the other hand, if I'm trying to break the world record in distance ski jumping the disadvantage of friction on the snow is that it slows down my acceleration down the slope and therefore reduces my end speed off the ski jump. The advantage of gravity is that it's pulling me ever faster down the slope to increase that end speed and lengthen my jump distance. As I said... it depends doesn't it?

Question:

Answers:advantage: friction, resistance offered to the movement of one body past another body with which it is in contact. In certain situations friction is desired. Without friction the wheels of a locomotive could not grip the rails nor could power be transmitted by belts. disadvantage: On the other hand, in the moving parts of machines a minimum of friction is desired; an excess of friction produces heat, which in turn causes expansion, the locking of the moving parts, and a consequent breakdown of the machinery. Lubrication is important in minimizing friction as are also such devices as ball and roller bearings.