The document discusses the concepts of forces and levers in mechanics, defining force as a push or pull and categorizing it into external and internal forces. It explains the three types of levers (1st, 2nd, and 3rd order), detailing their configurations, examples, and mechanical advantages or disadvantages. Additionally, it emphasizes the relationship between lever mechanics and angular displacement and velocity.

1. Dr Ashutosh Singh (PT)
Assistant Professor
Suresh Gyan Vihar University
Motion & Forces,Levers

2. A force is a push or a
pull exerted by one
object or substance on
another.
SI Unit - N (Newton)
FORCE

3. External
Types
External forces are pushes or
pulls on the body that arise
from sources outside the body
Internal
Internal forces are forces that
act on structures of the body
and arise from the body’s own
structures (i.e., the contact of
two structures within the
body).

4. LEVER
● A lever is a simple
machine consisting of a
rod suspended across a
pivot point
● Important function of a
lever is to convert the
force into torque.

5. ● Internal and External forces produce torques
throughout the body through a system of bony
levers.
● Imp forces involved are produced by muscles,
gravity and physical contact with the environment

6. 1st Order Lever
This is a type of lever which has
the fulcrum in between the
weight and the force applied.
Eg- Posture control of the head
in sagittal plane.

7. 1st Order Lever

8. 1st Order Lever

9. 1st Order Lever
Mechanical Advantage

11. First class levers may have an MA less
than 1, equal to 1, or more than 1

12. 2nd Order Lever
This is a type of lever
which has the weight in
between the fulcrum and
the force applied.
Eg - Standing on toes

13. 2nd Order Lever

14. 2nd Order Lever
2nd Order Lever always has the
moment arm more than 1. This is
why they are called lever of
Mechanical Advantage.

15. 3rd Order Lever
This is a type of lever
which has the effort/force
in between the weight
and the fulcrum applied.
Eg- Flexion of elbow

16. 3rd Order Lever

17. 3rd Order Lever
3rd Order Lever always has the
moment arm less than 1. This is why
they are called lever of Mechanical
Disadvantage/ speed.

18. Why lever of Speed ?
● All points throughout the lever share the
same angular displacement and velocity,
the more distal points on the arm move
at even greater displacement and
velocity.
● More the force more the velocity.

19. Q-1 Which type of lever has the fulcrum in between the weight
and effort?

20. Q-2 Identify Fulcrum?

21. THANK YOU