Fundamentals

1. 20ME205 – Engineering
Mechanics
( Core – II Subject)
Unit – I
Units & Dimensions, Laws of Mechanics
Date: 19 April 2021
A Presentation by:
Mr. R.L. SANKARLAL, M.E., MISTE., MSAE., (Ph.D).,
Asst. Professor (Gr-II) /Mech.,
R.M.K. Engineering College

2. Key Take Away points…
• Statics Vs Dynamics
• Rigid Body Vs Particle
• Definition of Force, Types.
• Components of Forces
• Equilibrium
• Resultant & Equilibrant
• Couple & Moment

3. Types of Forces
Concurrent coplanar
forces
Collinear forces
Concurrent non-coplanar
Non Concurrent coplanar
(Parallel)

4. Components of a Force
PlaneForce
SpaceForce

5. Couple Two equal and opposite forces are acting at
some distance forming a couple

6. How Rotational
Effect will change
with distance?

7. Free Body Diagram (FBD)
Isolated body from the structure of machinery which shows all the forces
and reaction forces acting on it.

8. Examples for free body diagram

14. Parallelogram law of Forces:
Two forces acting on a particle can be replaced by a single force
(RESULTANT) by drawing diagonal of the parallelogram which has the sides
equal to the given forces.

16. Triangle Law of Forces:
Triangle law states that if three concurrent coplanar forces are
acting at a point be represented in magnitude and direction by
the sides of a triangle, then they are in static equilibrium.

17. Lami’s Theorem:
Lami’s Theorem states that if three concurrent coplanar forces
are acting at a point, then each force is directly proportional to
the sine of the angle between the other two forces.

18. Lami’s theorem considering only
the equilibrium of three forces
acting on a point not the stress
acting through a ropes or strings
The principle of transmissibility is
applicable only for rigid bodies
not for deformable bodies

19. F1
F2
F5
F4
F3
A B
E
D
C
Polygon Law of Forces
“If many number of forces acting at
a point can be represented as a
sides of a polygon, then they are
in equilibrium”

20. Questions, Queries
& Discussions