6 Types Lever Pulley Wheel and axle Inclined Plane Screw Wedge
Lever A bar that is free to pivot about a fixed point (fulcrum) Fulcrum: the fixed point Effort arm: distance from the fulcrum to where the effort force is applied. Resistance arm: distance from the fulcrum to where the resistance force is applied
3 Classes of Levers 1 st class 2 nd class 3 rd class
First Class Lever Used to multiply force, always changes the direction of the applied force. Ex. Screwdriver used to pry paint can lid Fulcrum is in the middle
Second Class Lever Always multiplies force – does not change direction of force. Ex. Wheelbarrow Resistance is located between the effort force and the fulcrum
Third Class Lever Increases the distance over which the resistance force is applied. (Does not multiply force) Ex. Baseball bat or hockey stick Effort force is between the resistance force and the fulcrum.
Mechanical Advantage Lever IMA = length of effort arm length of resistance arm Making the effort arm longer increases the IMA.
Pulley Fixed Pulley: modified first class lever IMA = 1 Attached to ceiling or wall Changes direction Moveable Pulley: Multiplies force IMA = 2 Distance you pull is twice the resistance distance
Pulley (cont.) Block and Tackle System of fixed and moveable pulleys IMA = # of supporting ropes
Wheel and Axle Machine with 2 wheels of different sizes that rotate together (gears) Ex. Door knob IMA = radius of wheel radius of axle Can be increased by making the wheel larger
Inclined Planes Sloping surface Reduces the amount of force required IMA = length height *the longer the ramp the less force required
Screw Inclined plane wrapped around a cylinder. The closer together the threads, the easier to screw into wood
Wedge Inclined plane with one or two sloping sides Changes the direction of the effort force.
Compound Machine Two or more simple machines used together. Ex. Can opener Car