Simple machines include the inclined plane, lever, pulley, wheel and axle, and gears. A lever is a straight or bent bar that turns around a fixed point called the fulcrum. There are three classes of levers - class 1 levers multiply force but reduce speed, class 2 levers always multiply force, and class 3 levers always increase speed but reduce force. Examples of all three classes of levers can be found in the human body.

1. SIMPLE MACHINES

2. Simple
Machines
Inclined
plane
Screw
Wedge
Lever
Pulley
Wheel &
axle

3. Simple
Machines
Inclined
plane
Lever
Pulley
Gears

4. 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

5. KINDS OF LEVERS

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

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

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

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

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

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

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

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