SIMPLE MACHINES

Simple Machines

Inclined plane

Screw

Wedge

LeverPulley

Wheel & axle

Simple Machines

Inclined plane

LeverPulley

Gears

LEVERS

• Lever – straight/bent bar, turns about the fulcrum• Fulcrum (F) – axis about which the lever turns, fixed point• Effort arm• Load arm• Principle of a lever –

Moment of load about F = Moment of effort about F

Law of lever:

M.A. = Effort arm (derivation) Load arm

KINDS OF LEVERS

CLASS I LEVER (fulcrum)• Force multipliers - M.A. > 1, V.R. > 1 (greater effort arm)

CLASS I LEVER (fulcrum)• M.A. = 1, V.R. = 1 (effort arm = load arm)

CLASS I LEVER (fulcrum)• Gain in speed - M.A. < 1, V.R. < 1 (shorter effort arm)

CLASS I LEVER (fulcrum)• Examples in the human body

CLASS II LEVER (load)• Always force multipliers - M.A. > 1, V.R. > 1 (larger effort

arm always)

CLASS II LEVER (load)• Examples in the human body

CLASS III LEVER (effort)• Produce gain in speed always - M.A. < 1, V.R. <1 (shorter

effort arm always)

CLASS III LEVER (effort)• Examples in the human body