Basic of Engineering Mechanics; Engineering Mechanics ;fundamen; Forces; Particle; Force systems; Resultant Forces; Equilibrium of 2D forces; free body diagram; solved problems; solved numericals; examples etc.

1. Basics and Statics of
Particles
Lecture-01
CL-101 ENGINEERING MECHANICS
B. Tech Semester-I
Prof. Samirsinh P Parmar
Mail: samirddu@gmail.com
Asst. Professor, Department of Civil Engineering,
Faculty of Technology,
Dharmsinh Desai University, Nadiad-387001
Gujarat, INDIA

2. UNIT- I : Basics and Statics of Particles
CL-101 Engg. Mechanics, SPP, DoCL- DDU, Nadiad 2

3. Force
•Force is an agent which produces or tends to produce, destroys or
tends to destroy the motion of body or particles.
•Vector Quantity , Unit : Newton
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4. Forms and Characteristics of Forces
It has four characteristics
I. Direction
II. Magnitude
III. Point on which it acts
IV. Line of action
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5. Line of Action of force
•The line of action of a force f is a geometric representation of
how the force is applied.
•It is the line through the point at which the force is applied in the
same direction as the vector f→.
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6. System of forces
• Whentwo are or more forces acts act on a
• body, they are called system of forces.
1. Coplanar Force system – 2D and Non – Coplanar system – 3D
2. Concurrent and Non – Concurrent Force system
3. Collinear and Non- Collinear Force system
4. Parallel – Like and Unlike
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7. CL-101 Engg. Mechanics, SPP, DoCL- DDU, Nadiad 7

8. Coplanar Force System – 2D
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9. Non- Coplanar Force System – 3D
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10. Concurrent and Non – Concurrent Force
system
Concurrent Forces Non- Concurrent Forces
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11. Collinear and Non- Collinear Force
system
Collinear Forces Non – Collinear Forces
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12. Parallel Force system
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13. Examples
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14. Just Identify Force system
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15. Particle
•A Particle may be defined as a portion of a matter which is infinitely
small in size in all directions.
•It has no size, but it has mass
•Example : For astronomical Calculation, the earth may be assumed
to be particle.
•For mathematical description, a particle denotes a body in which all
the materials are concentrated at point.
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16. Resultant Force
•If a number of forces acting on a particle simultaneously
are replaced by a single force, which could produce the same effect
as produced by the given forces, that single force is called
Resultant Force.
•It is an equivalent force of all the given forces.
• Example:
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17. Example
•Find the resultant of force system shown in figure
Resultant Force
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18. Procedure
• Step 1 : Find algebraic sum of the horizontal
components
• Step 2 : Find algebraic sum of vertical
components
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19. Cont’d
• Step 3 : Find the magnitude of Resultant
force
• Step 4: Find the direction of Resultant Force
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20. Example:
Three coplanar concurrent forces are acting at a
point as shown in figure. Determine the resultant in
magnitude and direction.
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21. Cont’d
Four coplanar concurrent forces are acting at a point as shown in
figure. Determine the resultant in magnitude and direction.
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22. Equilibrium of Particle in 2D
•If the resultant of a number of forces acting on a particle is zero,
the particle is in equilibrium. The set of forces, where resultant is
zero, are called Equilibrium Forces.
•Equilibrant: (E) is equal to the resultant force (R) in magnitude and
direction, collinear but opposite in nature.
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23. Conditions of Equilibrium
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24. Example
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25. Free body Diagram (FBD)
•In equilibrium analysis of structures/machines. It is necessary to
consider all the forces acting on the body and exclude all the
forces which are not directly applied to it.
•The problem becomes much simple if each body is considered in
isolation. Such a body which has been so separated or isolated
from the surrounding bodies is called free body
•The sketch showing all the forces (both external and reaction) and
moments acting on the body is called as the free body diagram
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26. Action and Reaction
Example - FBD
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27. Example - FBD
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28. Example
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29. Example 2
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30. Resultant and Equilibrium of forces in 3D
(Non-Coplanar)
•Mainly used to convert force magnitude to force vector by
multiply with unit vector
.
•Methods used to express force as Cartesian vector:
• Three angles and force magnitude
 Coordinates and force magnitude
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31. 3D –Cartesian Coordinate system
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32. Type 1: Three angles Given
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33. CL-101 Engg. Mechanics, SPP, DoCL- DDU, Nadiad 33

34. Type 2: Coordinates and Force Magnitude
• Find coordinates with respect to origin
• Position vector = OP = (PO- OO)
• Unit vector = OP / mag of OP
• Force vector = Force magnitude x Unit vector
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35. Example
Find coordinates with respect to origin
Position vector = OP = (PO- OO)
Unit vector = OP / mag of OP
Force vector = Force magnitude x Unit vector
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36. Cont’d
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37. Cont’d
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38. 2D- Concurrent Force System
•Resultant of two concurrent forces
•It is calculated by Parallelogram law of forces
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39. CL-101 Engg. Mechanics, SPP, DoCL- DDU, Nadiad 39

40. 2D – Equilibrium
• Lami’s Theorem
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41. CL-101 Engg. Mechanics, SPP, DoCL- DDU, Nadiad 41