#### • Class 11 Physics Demo

Explore Related Concepts

#### Best Results From Wikipedia Yahoo Answers Youtube

From Wikipedia

In physics and engineering, mechanical advantage (MA) is the factor by which a mechanism multiplies the force or torque applied to it. Generally, the mechanical advantage is defined as follows:

MA = \frac{\text{output force}}{\text{input force}}

For an ideal (frictionless) mechanism, it is also equal to:

MA = \frac{\text{distance over which effort is applied}}{\text{distance over which the load is moved}}

For an ideal machine, the two equations can be combined, indicating that the force exerted IN to such a machine (denominator of first ratio) multiplied by the distance moved IN (numerator of second ratio) will equal the force exerted OUT of the machine multiplied by the distance moved OUT (i.e., work IN equals work OUT).

As an ideal example, using a block and tackle with 6 ropes, and a 600 pound load, the operator would be required to pull the rope 6 feet, and exert 100 pounds of force to lift the load 1 foot. Both equations show that the MA is 6. In the first equation, 100 pounds of force IN results in 600 pounds of force OUT. The second equation calculates only the ideal mechanical advantage (IMA) and ignores real world energy losses due to friction and other causes. Subtracting those losses from the IMA or using the first equation yields the actual mechanical advantage (AMA). The ratio of AMA to IMA is the mechanical efficiency of the system.

## Types

There are two types of mechanical advantage: ideal mechanical advantage (IMA) and actual mechanical advantage (AMA).

### Ideal mechanical advantage

The ideal mechanical advantage (IMA), or theoretical mechanical advantage, is the mechanical advantage of an ideal machine. It is calculated using physics principles because no ideal machine actually exists.

The IMA of a machine can be found with the following formula:

IMA = \frac {D_E} {D_R}

where

DEequals the 'effort distance' (for alever, the distance from the fulcrum to where the effort is applied)
DRequals theresistance distance (for a lever, the distance from the fulcrum to where the resistance is encountered)

### Actual mechanical advantage

The actual mechanical advantage (AMA) is the mechanical advantage of a real machine. Actual mechanical advantage takes into consideration real world factors such as energy lost in friction.

The AMA of a machine is calculated with the following formula:

AMA = \frac {R} {E_\text{actual}}

where

R = resistance force obtained from the machine
Eactual = actual effort force applied to the machine

## Simple machines

The following simple machines exhibit a mechanical advantage:

• The beam shown is in static equilibrium around the fulcrum. This is due to the moment created by vector force "A" counterclockwise (moment A*a) being in equilibrium with the moment created by vector force "B" clockwise (moment B*b). The relatively low vector force "B" is translated in a relatively high vector force "A". The force is thus increased in the ratio of the forces A : B, which is equal to the ratio of the distances to the fulcrum b : a. This ratio is called the mechanical advantage. This idealised situation does not take into account friction. For more explanation, see also lever.
• Wheel and axle motion (e.g. screwdrivers, doorknobs): A wheel is essentially a lever with one arm the distance between the axle and the outer point of the wheel, and the other the radius of the axle. Typically this is a fairly large difference, leading to a proportionately large mechanical advantage. This allows even simple wheels with wooden axles running in wooden blocks to still turn freely, because their friction is overwhelmed by the rotational force of the wheel multiplied by the mechanical advantage.
• Pulley: Pulleys change the direction of a tension force on a flexible material, e.g. a rope or cable. In addition, a block and tackle of multiple pulleys creates mechanical advantage, by having the flexible material looped over several pulleys in turn. Adding more loops and pulleys increases the mechanical advantage.
• Screw: A screw is essentially an inclined plane wrapped around a cylinder. The run over the rise of this inclined plane is the mechanical advantage of a screw.

### Pulleys

Consider lifting a weight with rope and pulleys. A rope looped through a pulley attached to a fixed spot, e.g. a barn roof rafter, and attached to the weight is called a single pulley. It has an MA = 1 (assuming frictionless bearings in the pulley), meaning no mechanical advantage (or disadvantage) however advantageous the change in direction may be.

A single movable pulley has an MA of 2 (assuming frictionless bearings in the pulley). Consider a pulley attached to a weight being lifted. A rope passes around it, with one end attached to a fixed point above, e.g. a barn roof rafter, and a pulling force is applied upward to the other end with the two lengths parallel. In this situation the distance the lifter must pull the rope becomes twice the distance the weight travels, allowing the force applied to be halved. Note: if an additional pulley is used to change the direction of the rope, e.g. the person doing the work wants to stand on the ground instead of on a rafter, the mechanical advantage is not increased.

By looping more ropes around more pulleys we can continue to increase the mechanical advantage. For example if we have two pulleys attached to the rafter, two pulleys attached to the weight, one end attached to the rafter, and someone standing on the rafter pulling the rope, we have a mechanical advantage of four. Again note: if we add another pulley so that someone may stand on the ground and pull down, we still have a mechanical a

Linebacker

A linebacker (LB) is a position in American football that was invented by football coach Fielding H. Yost of the University of Michigan. Linebackers are members of the defensive team, and line up approximately three to five yards (4 m) behind the line of scrimmage, behind the defensive linemen. Linebackers generally align themselves before the ball is snapped by standing upright in a "two point stance" (as opposed to the defensive linemen, who put one or two hands on the ground for a "three point stance" or "four point stance" before the ball is snapped).

## Types of linebackers

There are several different designations of linebackers: strongside, middle, and weakside. Usually the strongside and weakside are combined under the title outside, and the middle is renamed inside. In many formations and systems, teams do not use the strong and weakside designations, and merely play their outside linebackers consistently on one side of the formation and designate them either right outside linebacker and left outside linebacker. These terms are abbreviated ROLB and LOLB when appearing in lineup cards.

### Middle linebacker (MLB)

The middle linebacker, often referred to as "Mike," was invented by the Chicago Bears in the early 1950's. The Chicago Bears have also had the most successful middle linebackers in the NFL history. The Chicago Bears have had the most pro bowl middle linebackers in the NFL. The middle linebacker is often referred to as the "quarterback of the defense". Often it is the middle linebacker that receives the defensive play calls from the sideline and relays that play to the rest of the team&ndash;and in the NFL he is usually the defensive player with the electronic sideline communicator. A jack-of-all-trades, the middle linebacker can be asked to blitz (though they often blitz less than the outside linebacker), cover, spy the quarterback, or even have a deep middle-of-the-field responsibility in the Tampa 2 defense. In standard defenses, middle linebackers commonly lead the team in tackles.

### Outside linebacker (OLB)

The outside linebacker is usually responsible for outside containment. This includes the strongside and weakside designations below.

#### Strongside linebacker

The strongside linebacker (SLB) is often nicknamed "Sam" for purposes of calling a blitz. Since the strong side of the offensive team is the side on which the tight end lines up, or whichever side contains the most personnel, the strongside linebacker usually lines up across from the tight end. Often the strongside linebacker will be called upon to tackle the running back on a play, because the back will be following the tight end's block. He is most often the strongest linebacker; at the least he possesses the ability to withstand, shed, and fight off blocks from a tight end or fullback blocking the backside of a pass play. The linebacker should also have strong safety abilities in pass situation to cover the tight end in man on man situations. He should also have considerable quickness to read and get into coverage in zone situations.

#### Weakside linebacker

The weakside linebacker, or "Will", must be the fastest of the three, because he is often the one called into pass coverage. He is also usually chasing the play from the backside, so the ability to maneuver through traffic is a necessity for Will. Will usually aligns off the line of scrimmage at the same depth as Mike. Because of his position on the weakside, Will does not often have to face large interior linemen one on one unless one is pulling. In coverage, Will often covers the back that attacks his side of the field first in man coverage, while covering the weak flat or hook/curl areas in zone coverage. In a 3-4 defense the "Will" Linebacker plays on the "weakside" of the two middle Linebacker positions and a 4th Linebacker comes in to play the weakside. Known as a "Rush", "Rover", "Jack" and/or "Buck" Linebacker, their responsibility is more pass rush based but often is called into run stop (gap control) and pass coverage.

## Formations

The number of linebackers is dependent upon the formation called for in the play; formations can call for as few as none, or as many as seven. Most defensive schemes call for three or four, and they are named for the number of linemen, followed by the number of linebackers. For example, the 4-3 defense has four defensive linemen and three linebackers; conversely, the 3-4 defense has three linemen and four linebackers.

In the 4-3 defense there are four down linemen and three linebackers. The middle linebacker is designated "Mike" and two outside linebackers are designated "Sam" and "Will" according to how they line up against the offensive formation. If there is a strong call, the linebacker on the strongside is called "Sam", while the linebacker on the weakside is called "Will". The outside linebacker's job is to cover the end to make sure a run doesn't escape, and to watch the pass and protect from it. The middle linebacker's job is to stop runs between the tackles and watch the entire field to see the play develop. On pass plays, the linebackers' responsibilities vary based upon whether a man or zone coverage is called. In a zone coverage, the linebackers will generally drop into hook zones across the middle of the field. However, some zones will send the outside linebackers into the flats (area directly to the left and right of the hash marks, extending 4-5 yards downfield). In a man-to-man call, the "Sam" will often cover the tight end with help from a safety over the top, while at other times, the "Sam" and "Will" will be responsible for the first man out of the backfield on their side of the center, with the "Mike" covering if a second man exits on that side of the field.

In the "Tampa 2" zone defense the middle linebacker is required to drop quickly into a deep middle zone pass coverage thus requiring a quick player at this position.

### 3-4 defense

In the 3-4 Defense there are three lineman playing the line of scrimmage with four linebackers backing them up, typically two outside linebackers and two inside linebackers. The weak side inside linebacker is typically called the "Will," while the strong side or middle inside linebacker is called the "Mike". "Sam" is a common designation for strong outside linebacker, while the other position is usually called "Jack" and is often a hybrid DE/LB. Usually, teams that

Circuit theory

Circuit theory is the theory of accomplishing work by means of routing matter through a loop. The types of matter used are:

## Parts of a circuit

Every circuit consists of three basic components:

A gun, a rocket and an internal combustion engine all use compressed gas to do work, but the spent gas is vented to the atmosphere and is not reused in the system, so these are not examples of pneumatic circuits. Refrigeration systems do, however, recycle the compressed gases they use, but are not typically thought of as circuits.

Gears, levers, linkages, pulleys/ropes and sprockets/chains transmit work energy from one location to another, but there is no loop, so these are not examples of circuits.

## Circuit vs. network

An electrical circuit is a collection of electrical components which accomplish a specific task such as heating, lighting or running a motor. This collection may or may not form a complete topological loop, depending on whether it is presently connected to power, integrated into a larger device or circuit, or damaged. Sometimes, it is convenient to speak of an electrical circuit as a network, de-emphasizing the return path. Return paths are sometimes omitted from circuit diagrams, making the resulting graphic visually resemble a network topology rather than some sort of loop topology. See circuit diagram and schematic.

## Open circuit vs. closed circuit

A fundamental part of circuit analysis is determining whether the matter has a return path to the power source. If the matter is blocked from returning to the power source, either wholly or partially, the entire assemblage will be prevented from accomplishing work. In an electrical circuit, an open circuit is caused intentionally when a user opens a switch or unintentionally when vibration or mechanical damage severs a wire. In a pneumatic or hydraulic circuit, this occurs when a valve is closed or there is a leak in one of the lines or components.

In electrical circuits, closing a switch creates a closed loop for the electrons to flow through. This is sometimes referred to as "completing the circuit."

## Short circuit

In an electrical or electronic circuit, sometimes an unintended connection is made, such as when insulation is broken, frayed, melted or chewed by rodents, or a technician inserts a metal tool into a live device. When this happens, current bypasses some or all of the components in the circuit, taking a "shorter" path back to the power source. This can lead to excessive current drain, which in turn generates excessive heat, damaging or destroying sensitive parts of the system such as transistors and ICs.

## Loops

In Graph theory, an edge whose two ends meet is called a loop, which is an entirely different usage of the word. In any kind of circuit, such a loop has no distinct function. An argument can be made that redundant lines for transmission of power do have a function, even if it is only a backup function.

## Types

There are three basic types of circuit currently used in industry:

The following is a rough list of the types of components which make up each type of circuit.

### Hydraulic circuit

Question:1 meter 0.5 meter 0.25 meter none

Answers:The number of sheaves in the pulleys or blocks would be required and also the number of pulleys or blocks would need to be known in order to answer your question accurately. The minimum tackle you would need to lift 200N with 50N of force is a luff tackle rigged to advantage, but for simplicity let's just use a two-fold purchase or double tackle (two pulleys with two sheaves each). That would give you a purchase or lifting force of roughly 4 times (not counting friction) the pulling force. The velocity ratio of a block and tackle is always the same as the purchase or mechanical advantage of the system. In this case, the velocity ratio would be 4:1 just like the purchase, so 0.25 meters is the distance the moving block would travel per meter of the hauling part (end of rope you're pulling on).

Question:1) Inclined plane 2) Wedge 3) One lever (any class) 4) Wheel and axle 5) Fixed pulley 6) Moveable pulley 7) Block and tackle (MA 3)