2. Introduction
When person is moving his leg -
arms - any part of his body
He depend on his Skelton
system (muscle forces)
by contraction or extension
muscles.
In fact the bone in moving work
as A lever
Levers cannot be changed, but they
can be utilized more efficiently .
3. levers
Definition of levers
A rigid bar that turns about an axis of rotation or a
fulcrum .
Parts of a lever
- FulcrumAxis of rotation of the lever .
- Effort Arm The part of the lever that the effort force .
- Resistance Arm The part of thelever
that applies the resistance force .
4. Classification of levers
First Class Lever
A first-class lever is a lever in which the fulcrum (Axis) is located
between the input effort (Force) and the output load (Resistance).
Second Class Lever
Resistance (load) is located between the effort arm and the
fulcrum .
Third Class Lever
The effort force is located between the fulcrum and the resistance .
5. The 3 Classes of
Levers
| |
ForceArm |
A
R
F
| ForceArm | | ResistanceArm |
R
| Resistance Arm |
A
|
F
A
R
| ForceArm
ResistanceArm
F
|
• FAR
1st
• ARF
2nd
• AFR
3rd
6. 1 st class of lever in human body
The joint between the skull and the atlas vertebrae of the
spine the spine is the fulcrum across which muscles lift
the head .
7. The joint between the hummers and radius – ulna .
8. 2 nd class of lever in human body
The Achilles tendon, pushing or pulling across the heel of the foot.
9.
10. 3 rd class of lever in human body
The elbow joint: when lifting a book, the elbow joint is the
fulcrum across which the biceps muscle performs the work.
11.
12. Benefit from lever ?
Increase power
Increase distance
Increase speed
Transfer power from one place to another
precision in work safety
Avoid risks