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- Every Lever has three (3) parts:
- 1. Resistance Force, Input Force or Load, What you are trying to
move or lift.
- 2. Effort Force or Output Force - The work done on the Lever.
- 3. Fulcrum – A fixed pivot point.
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- The Fulcrum (fixed pivot point) is located between the Effort (Input)
and the Resistance (Output) Forces.
- The effort and the resistance move in opposite directions.
- The effort force pushes down in order to lift the resistance or load.
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- When the fulcrum is closer to the effort than to the load:
- there is a loss in force
- There is a gain in speed and distance.
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- When the fulcrum is closer to the load than to the effort:
- there is a loss in speed and
distance
- There is a gain in force.
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- When the fulcrum is midway between the effort and the load:
- there is no change in force,
speed or distance
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- The load is between the effort and the fulcrum.
- The fulcrum is at one end of the lever.
- The fulcrum is usually closer to the load.
- Produce a gain in force.
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- Examples:
- Wheelbarrow
- Bottle opener
- Nutcrackers
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- The effort is between the load and the fulcrum.
- There is usually a loss in force, but a gain in speed and distance.
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- A pulley changes the direction of the force:
- Instead of lifting up, you can pull down using your body weigh against
the load (what is being lifted)
- A pulley gains nothing in force, distance or speed
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- A pulley is a grooved wheel that turns around an axle (fulcrum), and a
rope or a chain is used in the grove to lift heavy objects.
- A pulley may be fixed, moveable, or used in combination.
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- Is attached to something that doesn't move such as the ceiling or wall)
- It acts as a first class lever with the fulcrum located at the axis
- Instead of a bar the pulley uses a rope or chain.
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- A moveable pulley acts as second class lever
- the load is between the fulcrum and the effort
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- A compound pulley is a system of movable pulleys.
- Mechanical advantage can be increased by using more than one pulley.
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- An inclined plane provides for NOT Less work but less effort.
- The trade off is greater distance to travel.
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- Used to reduce the force needed to overcome the force of gravity when
lifting or lowering a heavy object.
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- A Screw has two (2) parts:
- The Body – Cylinder Post
- The Thread – Inclined Plane wrapped around the cylinder.
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- Functions of the screw
- To fasten things – the standard screw or nuts & bolts.
- Drill bits are screws used to make holes.
- A jackscrew is used to lift heavy objects; car jack.
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- When you turn a screw:
- The input force is changed by the threads into an output force.
- The output force pulls the screw into the materials.
- Friction between the threads & the material holds the screw in
place.
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- The wedge used to increase force.
- The material remains in place while he wedge moves through it.
- A wedge changes the direction of the input force.
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- Wedges can be forced between two things to hold them tightly together,
like nails or a doorstop.
- Wedges can be used to split, cut or fasten.
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- The Wheel & axle is a modified lever:
- The center of the axle acts as a fulcrum – making the wheel a lever
that rotates around in a circle.
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