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 Machines are a device that allows you to do work in a way that is easier or more effective.  Ex. If you wanted to work on a house you could use a bulldozer.

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Presentation on theme: " Machines are a device that allows you to do work in a way that is easier or more effective.  Ex. If you wanted to work on a house you could use a bulldozer."— Presentation transcript:

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2  Machines are a device that allows you to do work in a way that is easier or more effective.  Ex. If you wanted to work on a house you could use a bulldozer to make part of the job go faster.

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4  A lever is a rigid rod that is free to rotate around a fixed pivot point  The fixed point that a lever rotates around is a fulcrum.

5  There are three classes of levers › These are defined by the location of the fulcrum relative to the effort force and resistance force › In a first class lever, the fulcrum is between the effort force and the resistance force › In a second class lever, the resistance force is between the effort force and the fulcrum › In a third class lever, the effort force is between the resistance force and the fulcrum

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7  A lever makes work easier by changing the amount of force exerted, the distance over which the force is exerted, or the direction of the force.  The effort you exert on a lever is called the effort force.  The distance you push down is the effort distance.  The force that the lever exerts on an object is called the resistance force.  The distance the lever pushes up on an object is the resistance distance.  The relationship between work done on a lever and the work does on a object is the formula: › EFFORT FORCE x EFFORT DISTANCE = RESISTANCE FORCE x RESISTANCE DISTANCE

8  A lever’s mechanical advantage is the number of times a lever increases a force exerted on it.  The mechanical advantage of a lever is equal to the ratio of resistance for to the effort force: › MECHANICAL ADVANTAGE= RESISTANCE FORCE/ EFFORT FORCE

9  The distance from the fulcrum to the effort force is called the effort arm  The distance from the fulcrum to the resistance force is the resistance arm.  The law of the lever states, that for a lever to be balanced, the effort force times the effort arm must be equal to the resistance force times the resistance arm.

10  Many of the body’s movable joints are actually fulcrums  The joints in the body act as pivot points for the bones  The bones act as levers, and muscles provide the force.  Your thigh, wrist, shoulder, knee, and elbow joint are all third class levers › The thigh and shoulder is an example of a ball and socket joint › Your wrist joint is an example of sliding joint › Your elbow and wrist joints are examples of hinge joints.

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12  The most common types of levers in your body is the third class lever.  But your body also has first and second class levers as well  There is always a lever where the effort force is applied at the point where a muscle attaches to a bone  The bone serves as a the lever, and the resistance force is the force exerted by the bone  The force may be used for many things like chewing, running, or lifting many things  Examples of different levers: › A first class lever is your neck › A second class lever is the call of your feet › A third class lever is your elbow

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