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Definition :

Definition The ratio of the force exerted by the machine to the force applied to the machine.

TWO TYPES OF MA :

TWO TYPES OF MA Ideal Mechanical Advantage (IMA) - the ideal or theoretical advantage afforded by using a machine (no friction) ACTUAL MECHANICAL ADVANTAGE (AMA) - the actual advantage afforded by using a machine minus friction.

EXAMPLE :

EXAMPLE If 400 N is used to move a 40 kg object but the machine allows the person to use 200 N to perform the job the IMA is IMA = force applied by the machine force applied to the machine = 400 N/200N = 2

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If instead the 400 N applied by the machine actually needs 200 N plus 50 N to overcome the friction applied to the machine, the AMA is AMA = 400N/250N = 1.6

EFFICIENCY :

EFFICIENCY Efficiency depends on reducing friction. A perfect machine with no friction has 100 % efficience since work out always equals work in. In the example before A machine uses 400 N to move an object 2m but the person applies 250 N to the machine over 4 m.

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Efficience = work out x 100% work in = 400 N x 2 m x 100% 250 N x 4 m = 800 J x 100 1000 J = 80 %

Mechanical Advantage using distance Mechanical advantage = input distance output distance Eg. A machine has a MA of 2.2 an output distance of 0.45 m. Find input distance.

SIMPLE MACHINES :

SIMPLE MACHINES 1. Lever:  A lever is a simple machine.  A lever is a board or bar that rests on a turning point.  This turning point is called the fulcrum.  An object that a lever moves is called the load.  The closer the object is to the fulcrum, the easier it is to move.

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THREE CLASSES OF LEVER      There are three classes of lever and each class has fulcrum, load and effort which together can move a heavy weight.   CLASS 1       The workman uses a trolley to move the large packing case. The fulcrum is the wheel.

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CLASS 2  The gardener uses a wheel barrow to lift tools and garden waste. The load is in the centre of the barrow

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CLASS 3    The fisherman catches the fish which becomes the load at the end of the lever.

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2.Inclined Plane:    An inclined plane is a simple machine.  It is a flat surface that is higher on one end.  You can use this machine to move an object to a lower or higher place.  Inclined planes make the work of moving things easier.  You would need less energy and force to move objects with an inclined plane.

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3.Wheel and Axle:  The wheel and axle is another simple machine.  The axle is a rod that goes through the wheel.  This lets the wheel turn.  It is easy to move things from place to place with wheels and axles.

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4. Screw:  A screw is a simple machine that is made from another simple machine.  It is actually an inclined plane that winds around itself.  A screw has ridges and is not smooth like a nail.  Some screws are used to lower and raise things.  They are also used to hold objects together.

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5.Wedge: A wedge is a simple machine used to push two objects apart.  A wedge is made up of two inclined planes.  These planes meet and form a sharp edge.  This edge can split things apart.

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6. Pulley: This simple machine is made up of a wheel and a rope.  The rope fits on the groove of the wheel.  One part of the rope is attached to the load.  When you pull on one side of the pulley, the wheel turns and the load will move.  Pulleys let you move loads up, down, or sideways.  Pulleys are good for moving objects to hard to reach places.  It also makes the work of moving heavy loads a lot easier