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From Wikipedia

Friction loss

Friction loss refers to that portion of pressure lost by fluids while moving through a pipe, hose, or other limited space. In mechanical systems such as internal combustion engines, it refers to the power lost overcoming the friction between two moving surfaces.

Friction loss has several causes, including:

  • Frictional losses depend on the conditions of flow and the physical properties of the system.
  • Movement of fluid molecules against each other
  • Movement of fluid molecules against the inside surface of a pipe or the like, particularly if the inside surface is rough, textured, or otherwise not smooth
  • Bends, kinks, and other sharp turns in hose or piping

In pipe flows the losses due to friction is of two kind first the skin-friction and the other is form-friction, the former one is due to the roughness in the inner part of the pipe where the fluid comes in the contact of the pipe material and the latter one is due to the obstructions present in the line of flow, it may be due to a bend or a control valve or anything which changes the course of motion of the flowing fluid.

Firefighting Applications

While friction loss has multiple applications, one of the most common is in the realm of firefighting. With the advent of modern power-takeoff (PTO) fire pumps, pressures created can sometimes overwhelm the ability of water to flow through a hose of a given diameter. As the velocity of water inside a hose increases, so does the friction loss. This resulting increase occurs as an exponential rate, thus an increase in the flow by a factor of X will result in an increase in friction loss by a factor of X2. For example, doubling the flow through a hose will quadruple the friction loss. Ultimately, as the pressure created by a fire pump goes higher and higher the amount of water actually flowing through a hose to a given point lessens, threatening firefighting operations. Conversely, friction loss can restrict the distance which water can be lifted during fire department drafting operations.

Formulas

The formula used most often in firefighting to express the amount of friction loss is:

FL = CQ2L

Where FL = friction loss (expressed in psi) C = coefficient of friction (based on the inside diameter of the hose and the inside jacket material) Q = flow rate in hundreds of gallons (gpm/100) L = Length of hose in hundreds of feet (L/100)



From Yahoo Answers

Question:School Project {again....}

Answers:a force is a push or a pull. examples of forces are kicking a football, lifting a table. advantages of friction is that you can walk without slipping everywhere and you can write on your paper. disadvantages are that it requires more effort to get work done, and there is heat, and friction may also cause wear and tear.

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:i dont want examples...... give me general answers....

Answers:1. friction opposes motion between two surfaces causing wear and tear 2. Without friction, motion is impossible 1 is a disadvantage while 2 is an advantage the major importance of friction is built on these two

Question:shot answers

Answers:Frictional force is neither advantageous nor disadvantageous intrinsically. The advantage or disadvantage comes not from the force, but from whether it helps or hinders the desired outcome. So, for example, it has advantages when it helps hold a ladder in place; so it doesn't slide out away from the wall. It has disadvantages when it pushes back against your attempt to shove a crate across the floor. You should be able to conjure up a pluses and minuses list on your own based on your own life's experiences.