Simple machines reduce effort, change the point and direction of applied effort, and can produce a gain in speed. They include levers, pulleys, wheels and axles, inclined planes, screws, and wedges. Simple machines work by transferring mechanical advantage, defined as the load divided by the effort. A mechanical advantage over 1 reduces effort but increases force (force multiplier), under 1 increases speed but decreases force. An advantage of 1 merely changes the direction of effort. Velocity ratio and efficiency are also defined.

1. Simple Machines

2. Simple machines:
• Reduce the effort (force multiplier)

3. Simple machines:
• Reduce the effort (force multiplier)
• Change point of application of effort to a
convenient point

4. Simple machines:
• Reduce the effort (force multiplier)
• Change point of application of effort to a
convenient point
• Change the direction of effort

5. Simple machines:
• Reduce the effort (force multiplier)
• Change point of application of effort to a
convenient point
• Change the direction of effort
• Produce a gain in speed

6. Simple machines:
• Reduce the effort (force multiplier)
• Change point of application of effort to a
convenient point
• Change the direction of effort
• Produce a gain in speed

7. • Load
• Effort
• Mechanical advantage, M.A. = Load (L)
Effort (E)
L > E - M.A. > 1 – force multiplier
E > L - M.A. < 1 – gain in speed
E = L - M.A. = 1 – changes direction of effort
(no change in force/speed)
Units
Technical terms

8. • Velocity ratio, V.R. = Velocity of effort (VE)
Velocity of load (VL)
V.R. = dE/t
dL/t
V.R. = dE
dL
dE > dL – V.R. > 1 – force multiplier
dL > dE – V.R. < 1 – gain in speed
dL = dE – V.R. = 1 – changes direction of effort
(no change in force/speed)
Units
Technical terms

9. Technical terms
• Work input
• Work output
MachineEffort LoadWork
input
Work
output

10. Technical terms
• Work input
• Work output
MachineEffort LoadWork
input
Work output

11. Technical terms
• Work input
• Work output
MachineEffort Load
Work input
Work output

12. Technical terms
• Work input
• Work output
MachineEffort Load
Work input
Work output
Efficiency, η =

13. Technical terms
• Work input
• Work output
MachineEffort Load
Work input
Work output
Efficiency, η =
Units

14. Technical terms
• Effort point
• Load point
• Input energy
• Output energy
• Principle of a machine
• Relation between M.A., V.R. and η