1. Biomechanics
Principles of Levers

2. Principles of Levers Aim:
To understand how the three types of levers work and appreciate the advantages/disadvantages of each one.

3. Principles of Levers
Expected Knowledge
Force
Velocity

4. Principles of Levers
Key Vocabulary
Lever
Fulcrum
Resistance
Effort

5. Levers are… Simple machines that help us apply force.
Rigid structures, hinged at some part with forces applied at two other points.

6. We have levers within our body, and also
use them externally for many different
reasons.

7. All levers have three parts:
Fulcrum
Resistance
Effort

8. Fulcrum
The pivot point.

9. The weight that needs to be moved.
Resistance (or load)
The weight that needs to be moved.

10. The force that is applied to move the resistance (or load).
Effort
The force that is applied to move the resistance (or load).

11. Levers perform two main functions:
Functions of a Lever
Levers perform two main functions:
To increase the resistance
(or force) that can be moved with
a given effort e.g. a crowbar.
To increase the velocity at
which an object will move with a
given force. E.g. A golf club.

12. Classes of Levers There are 3 classes of levers.
Each is structured in a different manner and has different advantages.

13. The fulcrum lies between the effort and the resistance.
First Class Levers
The fulcrum lies between the effort and the resistance.

14. First Class Levers
Using a crowbar to move a rock.

15. First Class Levers
Using a hammer to pull out a nail.

16. First Class Levers
A see-saw.

17. Up and down movement of the head about the atlas joint.
First Class Levers
Up and down movement of the head about the atlas joint.

18. Pulling an oar in a row boat.
First Class Levers
Pulling an oar in a row boat.

19. The resistance lies between the fulcrum and the point of effort.
Second Class Levers
The resistance lies between the fulcrum and the point of effort.

20. The movement of the foot when walking.
Second Class Levers
The movement of the foot when walking.
(the calf muscle provides the effort and the ball of the foot is the pivot)

21. Opening a door by the handle.
Second Class Levers
Opening a door by the handle.

22. Second Class Levers
Opening a bottle with a bottle opener.

23. Second Class Levers
Pushing a wheel barrow.

24. The effort lies between the resistance and the fulcrum.
Third Class Levers
The effort lies between the resistance and the fulcrum.

25. Third Class Levers
Biceps curl.

26. Third Class Levers
Fishing with a rod.

27. Third Class Levers
Swinging a bat to hit a ball.

28. Application provide amplified power at the Long levers
expense of speed of movement of the object being moved.
Examples:
Using a jack to lift a crashed car.
Using a knife to get the lid off a tin.

29. Application Short levers provide speed at the expense of power
Example:
Levers designed to accelerate objects include:
- Most body limbs used for throwing or kicking
because the muscle inserts near the pivot
point.

30. Application
Can you think of sporting examples where there are longer and shorter levers?
What happens to the effectiveness of a lever if the fulcrum is moved closer or further away from the load?

31. Revision Question One: Fill in the blanks
Levers are simple machines which helps us apply
____(a)____ . They have ___(b)___ parts. The ___(c)___
is the pivot point. The ___(d)___ (or load) is the weight that
needs to be moved. The ___(e)___ is the force that is
applied to move the resistance.

32. Revision
Question Two: Label the diagram

33. Revision Question Three: First, Second or Third Class? (a) (b) (c)
The effort lies between the resistance and the fulcrum.
The fulcrum lies between the effort and the resistance.
The resistance lies between the fulcrum and the point of effort.

34. Revision
Question Three: First, Second or Third Class?
(d) (e)
(f)

35. Revision
Question Three: First, Second or Third Class?
(g) (h)
(i) (j)

36. Revision
Question Three: First, Second or Third Class?
(k) (l)
(m) (n)

37. Application
How would you change your grip on a softball bat if you wanted to hit the ball with more force? Experiment with this with a partner.
With a partner find another physical activity example that will be able to demonstrate application of the principles of levers, showing what happens when you change the length of your lever.