lever,pulleys.pdf

For knowledge of biomechanics

1. UNIT -2:LEVERS, WHEEL AXIS
AND PULLY

2. CONTENTS OF THE PRESENTATION
•Simple Machine intro
•Mechanical advantage and ideal M.A
•Levers
•Wheel and Axle
•Pulley

3. SIMPLE MACHINE: INTRO
•Any mechanical device that makes life easier.
•It modifies the direction and magnitude of motion and
force to perform work.

4. MECHANICAL ADVANTAGE
•“How much advantage does a simple machine
provides for the execution of work?”
•Mechanical Advantage:

Output force or Load overcame
Input force or Force applied

•Values= >1,1,<1

5. IDEAL MECHANICAL ADVANTAGE
•Found in ideal machine.
•Always more than actual mechanical advantage.

Input distance
Output distance

6. LEVERS
•A rigid bar which turns above an axis or fulcrum or pivot
in response to effort or Force to overcome a load or
Resistence
•It has three points
R or L
Axis/fulcrum/pivot
E or F

7. LEVERS(CONTD.)
•In anatomical levers:

Bone = bars

Muscle insertion= effort

joints= axis

Segments or
COM of the = Resistence
segments

8. LEVERS- MECHANICAL ADVANTAGE
•It’s mechanical advantage


Effort Arm
Load Arm

9. TYPES OF LEVERS

10. LEVERS: FIRST CLASS LEVER
•Axis near middle = balance movement
•Axis near load = force motion
•Axis near force= speed and range of motion

11. LEVERS-SECOND CLASS
•Suitable for force motion.

12. LEVERS- THIRD CLASS
•Speed and range of motion movement

13. WHEEL AND AXLE
A kind of simple machine where a larger circular
frame(wheels) revolves around a shaft or rod(axle).
Properties of wheel and axle:
•Both turn at the same time.
•Center of both=Fulcrum
•Radius of both can act as
Effort arm.

These enhance ROM and
Speed of movement in
The musculoskeletal system.

14. WHEEL AND AXLE: TYPES
Point of force application on Wheel
•Radius of wheel = Effort arm
•Radius of Axle = Load arm
•Mechanical Advantage= Radius of Wheel
Radius of Axle

•It’s value= >1

15. WHEEL AND AXLE: TYPES (CONTD.)
•External rotation of the shoulder.

16. WHEEL AND AXLE: TYPES(CONTD.)
Point of force application on axle
•Radius of axle = Effort arm
•Radius of wheel = Load arm
•Mechanical Advantage= Radius of Axle
Radius of Wheel

•It’s value= <1

•But, known as
“Movement Amplifier”

17. WHEEL AND AXLE: TYPES(CONTD.)

18. PULLEY
•A form of wheel and axle.
•Here, axle is fixed and a rope or belt or cord is passed
over the wheel.
•Wheel turns on the axis.
•Like levers, it also multiplies force or changes its direction
of force application.

19. PULLEY(CONTD.)

20. PULLEY:TYPES
•There are three types of pulleys:
Fixed single Pulley
Movable single Pulley
Compound Pulley

21. PULLEY: FIXED SINGLE PULLEY
•Mechanical advantage of Single Pulley= 1.

•Only changes the
direction of force.

•Acts like Class 1 lever

22. PULLEY: MOVEABLE SINGLE PULLEY
•It’s mechanical advantage = 2.

•It amplifies input force.

•Acts like a Class 2 lever

23. PULLEY: COMPOUND PULLEY
•A combination of moveable and fixed pulleys.
•Various types of compound pulleys are available.

•Every additional rope attached
to the moveable pulley or
strand of rope supporting it
increases the M.A by 1.

24. ANATOMICAL PULLEY
•In the human body,
Bones, ligament or cartilage = Pulley
Tendon = cord
•Tendons slide over the pulley(bone, ligament or
cartilage).
•Their function:
to redirect and deflect the action line of muscle
away from the joint axis to increase the M.A of the
muscle force.

25. CLASSIFICATION OF ANATOMICAL
PULLEY
There are four kinds of Pulleys(3 fixed, 1 moveable)

•Class 1 pulley(fixed.)

•Class 2 pulley(fixed)

• Class 3 pulley (fixed)

•Class 4 pulley (moveable)

26. CLASS 1 PULLEY
•It is a fixed pulley.
•It complements the action of muscle.
•Tendon passes over an external support which serves
as pulley.

•Ex. Patella.

27. CLASS 2 PULLEY
•These alter the action of the muscle at the joints,
•It has subtypes:
•Pulley= Bone
ex. Lateral
malleolus

28. CLASS 2 PULLEY
•Pulley = Cartilage(ex. Trochlea in eye)

29. CLASS 2 PULLEY
•Pulley= ligament
•Ex. Flexor retinaculum

30. CLASS 3 PULLEY
•Here, Joint serves as Pulley.

•Ex. Shoulder joint.

31. CLASS 4 PULLEY
•It is combined pulley.
•Here, Muscle acts a pulley
for another pulley(muscle.)

•Ex. Biceps muscle passing
over brachialis muscle.

32. REFERENCES
•https://www.britannica.com/technology/simple-
machine
•https://hemantmore.org.in/foundation/science/physi
cs/simple-machines/344/
•https://www.britannica.com/technology/mechanical
-advantage
•Floyed ,R.T.(2009). manual of structural
kinesiology.,USA,ed.16. humankinetics
•www.kau.edu.sa/Files/0057413/Files/86960_PULLEYS.PP
T
•https://www.slideshare.net/ainaa123/fixed-pulley

33. Thank You