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Work and Simple Work and Simple MachinesMachines

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Simple MachinesSimple Machines A machine is a device that helps make A machine is a device that helps make

work easier to perform by accomplishing work easier to perform by accomplishing one or more of the following functions: one or more of the following functions: transferring a force from one place to another, transferring a force from one place to another, changing the direction of a force, changing the direction of a force, increasing the magnitude of a force, or increasing the magnitude of a force, or increasing the distance or speed of a force. increasing the distance or speed of a force.

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First Class LeverFirst Class Lever In a first-class lever the fulcrum is located In a first-class lever the fulcrum is located

at some point between the effort and at some point between the effort and resistance forces.resistance forces. Common examples of first-class levers Common examples of first-class levers

include crowbars, scissors, pliers, tin snips include crowbars, scissors, pliers, tin snips and seesaws. and seesaws.

A first-class lever always changes the A first-class lever always changes the direction of force (I.e. a downward effort force direction of force (I.e. a downward effort force on the lever results in an upward movement on the lever results in an upward movement of the resistance force). of the resistance force).

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Fulcrum is between EF (effort) and RF (load)Fulcrum is between EF (effort) and RF (load)Effort moves farther than Resistance.Effort moves farther than Resistance. Multiplies EF and changes its direction Multiplies EF and changes its direction

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Second Class LeverSecond Class Lever With a second-class lever, the load is located With a second-class lever, the load is located

between the fulcrum and the effort force.between the fulcrum and the effort force. Common examples of second-class levers Common examples of second-class levers

include nut crackers, wheel barrows, doors, and include nut crackers, wheel barrows, doors, and bottle openers.bottle openers.

A second-class lever does not change the A second-class lever does not change the direction of force. When the fulcrum is located direction of force. When the fulcrum is located closer to the load than to the effort force, an closer to the load than to the effort force, an increase in force (mechanical advantage) increase in force (mechanical advantage) results. results.

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RF (load) is between fulcrum and EF RF (load) is between fulcrum and EF Effort moves farther than Resistance.Effort moves farther than Resistance.

Multiplies EF, but does not change its directionMultiplies EF, but does not change its direction

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Third Class LeverThird Class Lever With a third-class lever, the effort force is With a third-class lever, the effort force is

applied between the fulcrum and the applied between the fulcrum and the resistance force.resistance force. Examples of third-class levers include Examples of third-class levers include

tweezers, hammers, and shovels.tweezers, hammers, and shovels. A third-class lever does not change the A third-class lever does not change the

direction of force; third-class levers always direction of force; third-class levers always produce a gain in speed and distance and a produce a gain in speed and distance and a corresponding decrease in force. corresponding decrease in force.

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EF is between fulcrum and RF (load) EF is between fulcrum and RF (load) Does not multiply force Does not multiply force

Resistance moves farther than Effort.Resistance moves farther than Effort.

Multiplies the distance the effort force travelsMultiplies the distance the effort force travels

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Wheel and AxleWheel and Axle The wheel and axle is a The wheel and axle is a

simple machine simple machine consisting of a large consisting of a large wheel rigidly secured to a wheel rigidly secured to a smaller wheel or shaft, smaller wheel or shaft, called an axle. called an axle.

When either the wheel or When either the wheel or axle turns, the other part axle turns, the other part also turns. One full also turns. One full revolution of either part revolution of either part causes one full revolution causes one full revolution of the other part. of the other part.

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PulleyPulley A pulley consists of a grooved wheel that A pulley consists of a grooved wheel that

turns freely in a frame called a block.turns freely in a frame called a block. A pulley can be used to simply change the A pulley can be used to simply change the

direction of a force or to gain a mechanical direction of a force or to gain a mechanical advantage, depending on how the pulley is advantage, depending on how the pulley is arranged. arranged.

A pulley is said to be a A pulley is said to be a fixed pulleyfixed pulley if it does if it does not rise or fall with the load being moved. A not rise or fall with the load being moved. A fixed pulley changes the direction of a force; fixed pulley changes the direction of a force; however, it does not create a mechanical however, it does not create a mechanical advantage. advantage.

A A moveable pulleymoveable pulley rises and falls with the rises and falls with the load that is being moved. A single moveable load that is being moved. A single moveable pulley creates a mechanical advantage; pulley creates a mechanical advantage; however, it does not change the direction of however, it does not change the direction of a force. a force.

The mechanical advantage of a moveable The mechanical advantage of a moveable pulley is equal to the number of ropes that pulley is equal to the number of ropes that support the moveable pulley. support the moveable pulley.

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Inclined PlaneInclined Plane An inclined plane is An inclined plane is

an even sloping an even sloping surface. The inclined surface. The inclined plane makes it easier plane makes it easier to move a weight from to move a weight from a lower to higher a lower to higher elevation.elevation.

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Inclined PlaneInclined Plane The mechanical The mechanical

advantage of an inclined advantage of an inclined plane is equal to the plane is equal to the length of the slope length of the slope divided by the height of divided by the height of the inclined plane. the inclined plane.

While the inclined plane While the inclined plane produces a mechanical produces a mechanical advantage, it does so by advantage, it does so by increasing the distance increasing the distance through which the force through which the force must move. must move.