1. Simple body
machines

2. Simple body machines 1- Levers. 2- Pullys. 3- Wheel and axle.
Musculoskeletel system arrangement provides for 3 types of machines in producing movement:
1- Levers.
2- Pullys.
3- Wheel and axle.

3. Pulley is a simple machine, that performs a mechanical job.
Definition
Pulley is a simple machine, that performs a mechanical job.
It consists of a grooved wheel and a cord or a rope running over it.

4. Types of pulleys
1. Fixed pulley
2. Mobile pulley
3. Mixed pulley

5. Fixed pulley It is the only example of pulley in human body
A fixed pulley changes the direction of a force.
Mechanical advantage = 1

6. mobile pulley It is used in exercises.
The mechanical advantage of a mobile pulley is equal to the number of ropes that support the mobile pulley.

7. Mixed pulley It is used in exercises.
The combination between fixed and mobile pulleys.
Mixed pulleys acts to increase mechanical advantage.
Each additional rope increases mechanical advantage by 1.

8. Functions of pulleys Change direction of force Balance of force
Modify the effect of a force
Magnify the force via increasing the MA

9. 1. Wheel: Represented by bony component which can be
Human equivalents
1. Wheel: Represented by bony component which can be
External bone: as patella
Bony prominence: as condyles, trochanters, tuberosities
2. Rope or Cord: is represented by tendon, muscle, musculotendinous junction.

10. Patella as a pulley
Patella acts as an external pulley for the tendon of quadriceps muscle tendon

11. Patella as a pulley

12. Patella has the following functions
Move the muscle away
Increase the moment arm
Increase the quadriceps torque
Patella has the following functions
Increase the angle of pull
Increase the rotatory component
Increase the efficiency of quadriceps muscle
Improve the mechanical advantage

13. Lateral malleolus bone as a pulley
lateral malleolus acts as a pulley around which tendon of peroneus longus runs.
As peroneus longus contracts, it pulls toward it belly (toward the knee).
Using the lateral malleolus as a pulley, force is transmitted to plantar aspect of foot resulting in eversion/plantarflexion.

14. Wheel and axle
Center of the wheel & the axle both correspond to the fulcrum
Both the radius of the wheel & the radius of the axle correspond to the force arms

15. Wheel and axle
When either the wheel or axle turn, the other must turn as well
Both complete one turn at the same time

16. Wheel and axle
If the wheel radius is greater than the radius of the axle, then, due to the longer force arm, the wheel has a mechanical advantage over the axle
a relatively smaller force may be applied to the wheel to move a relatively greater resistance applied to the axle
if the radius of the wheel is 3 times the radius of the axle, then the wheel has a 3 to 1 mechanical advantage over the axle

17. Wheel and axle
calculate mechanical advantage of a wheel & axle by considering the radius of the wheel over the axle
Mechanical radius of the wheel
advantage = radius of the axle
Mechanical
advantage = 1

18. Wheel and axle
If application of force is reversed and applied to the axle, then the mechanical advantage results from the wheel turning a greater distance & speed
if the radius of the wheel is 3 times the radius of the axle, then outside of the wheel will turn at a speed 3 times that of the axle.
the distance that the outside of the wheel turns will be 3 times that of the outside of the axle.

19. Wheel and axle Mechanical radius of the axle
Calculate the mechanical advantage for this example by considering the radius of the wheel over the axle
Mechanical radius of the axle
advantage = radius of the wheel
Mechanical
advantage = 3

20. Wheel and axle
Used primarily to enhance range of motion & speed of movement in the musculoskeletal system
function essentially as a form of a lever
Ex. resulting in greater range of motion & speed is with upper extremity in internal rotators attaching to humerus:
Humerus acts as the axle.
Hand & wrist are located at the outside of the wheel when elbow is flexed 90 degrees.
With minimal humerus rotation, the hand & wrist travel a great distance.
Allows us significantly increase the speed at which we can throw objects.

21. The 6 Simple Machines Pulley Lever Wheel and Axle Inclined Plane Screw
Wedge

22. Inclined Planes
An inclined plane is a flat surface that is higher on one end.
Inclined planes make the work of moving things easier.

23. Inclined Planes Work input: is the amount of work on a machine.
Input force x input distance
Work output: is the amount of work done by a machine.
Output force x output distance
Work out = Work in
F out x D out = F in x D in
10 N x 3 m = 2 N x 15 m
D in
15 m
D out
3 m
F in
F out 10 N

24. length of the slope height of the inclined plane
Mechanical Advantage (MA)
Definition
It is the way to measure the efficiency of this machine that means the ability of the machine to magnify force or to increase the output in relation to the input.
Mechanical advantage of the inclined plane =
length of the slope height of the inclined plane

25. Inclined Plane Mechanical Advantage
The mechanical advantage of an inclined plane is equal to the length of the slope divided by the height of the inclined plane.
While the inclined plane produces a mechanical advantage, it does so by increasing the distance through which the force must move.

26. Inclined Plane Mechanical Advantage
Sloping surface used to lift heavy loads with less effort

27. A screw is an inclined plane wound around a central cylinder

28. Wedges Two inclined planes joined back to back.
Wedges are used to split things.

29. Wedges
Converts motion in one direction into a splitting motion that acts at right angles to the blade.

30. Wedges Wedges change the direction of an applied force.
When force is applied downward on a wedge, it distributes the force outward in two directions, separating a material.

31. Wedges Mechanical Advantage
The mechanical advantage of a wedge can be found by dividing the length of either slope (S) by the thickness (T) of the big end.
As with the inclined plane, the mechanical advantage gained by using a wedge requires a corresponding increase in distance.

32. Compound Machine
Bowflex: Pulley lifts the weight, the seat is an inclined plane, and the lever is what you pull to adjust the seat.

33. THANK YOU