Levers
Essay by people • August 4, 2011 • Essay • 559 Words (3 Pages) • 2,455 Views
Levers!
A lever :is a bar that is free to pivot or turn around a fixed point.
The fixed point of a lever pivots on is called the fulcrum. The input arm of the lever is the distance from the fulcrum to the point where input force is is applied. The output arm is the distance from the fulcrum to the point where the output force is exerted by the lever.
Output force of a lever depends on the length of the input arm and the output arm.
The differences of the three classes of levers depends on locations, of the fulcrum, input and output force.
First class levers
For a first class lever, the fulcrum is located between the input and output forces. The output force is always in the opposite direction to the input and output lever.
Second class lever
For a second class lever the output force is located between the input force and the fulcrum.
Third class lever
The input force is applied between the output force and the fulcrum.
Ideal MA of a lever
IMA = L in
L out
Pulleys!
Pulley= is a grooved wheel with a rope, chain, or cable running along the groove, a fixed pulley is a modified first class lever.
A system of pulley's can change the direction of the input force and make it longer.
Movable pulleys
A pulley in which one end of the rope is fixed and the wheel is free to move is called a movable pulley.
A movable pulley does not multiply force.
For a movable pulley, the distance you pull the rope upward is twice the distance the weight moves upward.
The block and tackle
A system of pulleys consisting of fixed and movable pulleys isa called a block and tackle.
The IMA of a pulley system is equal to the number of rope segments that support the weight.
Wheel and axle
Wheel and axle= is a simple machine consisting of a shaft or axle attached to the center of a larger wheel, so that the wheel and axle rotate together .
Doorknobs screw drivers, and faucet handles are examples of wheel and axles.
Mechanical advantage of an wheel and axle
A wheel and axle is another modified lever. The center of an axle is the fulcrum.
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