1. MEC201 Mechanics of Solids

2. Lecture 2
Fluid Mechanics is the study of the motion of the fluids, the forces that result from such motion, and the forces required to cause such motion.
We are surrounded by fluids all around us. The motions of air in our atmosphere and water in our ocean and river determine the weather, so essential for life on earth.
In fact we are concerned with motion of fluids in a more intimate manner as well. The flow of blood in our veins and arteries, of the other bodily fluids, of air that we breathe are all necessary for maintaining life.

3. Resultant of Forces
Law of Parallelogram of forces:

4. Resultant of Forces
Triangle of forces of forces:

5. Resolving a force

6. Force as a Vector F = Fx i + Fy j + Fz k y Fx Fy Fz F = x z

7. Addition of Forces F2 = Fx2 i + Fy2 j
R = F1 + F = (F1x + F2x)i + (F1y + F2y) j

8. Example

9. Turning Effect of a Force: Momentsd
The tuning effect of a force is measured by the moment Fd

10. Moment/ Torque

11. Moment is a Vector F r ●
M = r× F
Right-Hand Rule

12. Example

13. Determining Moments in 2D
Right Hand Rule: ● ×

14. Equilibrium
Fluid Mechanics is the study of the motion of the fluids, the forces that result from such motion, and the forces required to cause such motion.
We are surrounded by fluids all around us. The motions of air in our atmosphere and water in our ocean and river determine the weather, so essential for life on earth.
In fact we are concerned with motion of fluids in a more intimate manner as well. The flow of blood in our veins and arteries, of the other bodily fluids, of air that we breathe are all necessary for maintaining life.

15. Equilibrium System does not accelerate Consequence of first law
No net force.

16. Is That Enough?
It will rotate till the two forces are in line.

17. Equilibrium
For a particle: ∑F = 0 For a rigid body: ∑F = 0, ∑M = 0

18. Equilibrium
∑F = 0 ∑ Fx = 0; ∑ Fy = 0; ∑ Fz = 0 ∑M = 0 ∑ Mx = 0; ∑ My = 0; ∑ Mz = 0

19. Free-body Diagrams
Fluid Mechanics is the study of the motion of the fluids, the forces that result from such motion, and the forces required to cause such motion.
We are surrounded by fluids all around us. The motions of air in our atmosphere and water in our ocean and river determine the weather, so essential for life on earth.
In fact we are concerned with motion of fluids in a more intimate manner as well. The flow of blood in our veins and arteries, of the other bodily fluids, of air that we breathe are all necessary for maintaining life.

20. Free-Body Diagrams (FBD)
A free-body diagram of a structure or a part of the structure removed from its support.
It shows all the (external) forces acting on that part of the structure.
The supports are replaced by the forces that the supports apply on the structure.

21. Free-Body Diagram (FBD)

22. Free-Body Diagrams (FBD)...
Tension in the rope ?? T
T = W W

23. Free-Body Diagrams (FBD)...
300 N
250 N
? N
∑F = 0
? = 250 N

24. Free-Body Diagrams (FBD)...
Tension ? T
300 N
250 N
T = 800 N

25. Lifting Pulley Block T
T = W/4
Mechanical Advantage W