Mekanika Fluida FM01 (Lecture2: 4/4). Tekanan pada Dinding Bejana

Summary

The transcript discusses the mechanics of force and pressure on a dam structure, explaining how to calculate the forces acting on a wall submerged in fluid. Key topics include pressure reference points, the difference between absolute and gauge pressures, and the integral calculus needed to compute forces in fluid mechanics. The speaker explores how pressure varies with height and how forces apply to small segments of the structure, ultimately leading to an overall calculation of the total force exerted on the dam. The content involves both theoretical and practical elements of fluid dynamics and engineering principles.

Takeaways

• 😀 The video discusses the concept of force and pressure in the context of dam construction, focusing on how to design a dam to withstand fluid pressure.
• 😀 The dam construction involves four individuals and artificial walls, with the goal of determining the pressure needed to resist the fluid on the left side of the dam.
• 😀 The concept of pressure is explored, referencing key pressure points in the dam design, especially considering atmospheric pressure and its influence on the fluid.
• 😀 The script mentions the importance of defining a reference pressure, which can be either absolute or gauge pressure, to understand the pressure differences.
• 😀 The pressure in a system is described as relative to atmospheric pressure, with gauge pressure being positive or negative depending on whether the pressure is higher or lower than atmospheric pressure.
• 😀 The design of the dam involves calculating the total force exerted by the pressure of the fluid, which varies with height, and how this force impacts the structure.
• 😀 The pressure increases with depth, and the script emphasizes the need to consider small domains to calculate the force over a particular section of the dam wall.
• 😀 The formula for calculating the force involves multiplying the pressure by the area of a thin strip (domain) on the dam's surface.
• 😀 A key point in the design process is understanding the direction of the force, which is always normal (perpendicular) to the surface of the dam wall.
• 😀 The script concludes with a discussion about how forces are integrated over the entire dam surface, leading to the total force, and references to calculus for calculating these values.

Q & A

What is the primary topic discussed in the transcript?

The transcript primarily discusses fluid mechanics, specifically the forces and pressures acting on a dam or structure, and the relationship between pressure and force in such scenarios.

What is the role of pressure in the context of the dam's design?

Pressure plays a key role in determining the structural requirements for a dam. The pressure from the fluid acting on the dam's wall must be accounted for to ensure the dam can withstand the force and prevent failure.

What does the term 'P absolute' refer to in the context of the transcript?

'P absolute' refers to the absolute pressure, which is the total pressure at a given point, including atmospheric pressure. It is used to differentiate from gauge pressure, which is relative to atmospheric pressure.

How does atmospheric pressure affect the calculations in the script?

Atmospheric pressure is considered as the reference point when calculating pressures within the system. It establishes the baseline for determining whether the pressure is positive or negative, depending on whether it exceeds or falls below atmospheric pressure.

What is the significance of the 'gauge pressure' mentioned in the transcript?

Gauge pressure is the pressure relative to atmospheric pressure. It is commonly used to measure the internal pressure of things like tire or bicycle pumps and can be negative when the pressure at a given point is lower than atmospheric pressure.

What does the term 'normal force' refer to in this context?

Normal force refers to the force that acts perpendicular (normal) to the surface of the dam wall due to the pressure exerted by the fluid. This force is critical in designing the structure to withstand the fluid's pressure.

What is the role of the integral in the calculation of force?

The integral is used to calculate the total force acting on the dam by summing up the small forces (differential forces) across different heights or sections of the dam. The integral accounts for the variation in pressure with depth.

How does the pressure vary with height in the fluid?

The pressure increases with height in the fluid due to the weight of the fluid above. This relationship is fundamental in calculating the total pressure and force exerted on a submerged surface.

What is meant by 'domain' in the transcript?

The 'domain' refers to a small section or segment of the dam or the fluid where forces and pressures are calculated. The domain is used to simplify the analysis by considering small, manageable sections rather than the whole structure at once.

How is the concept of 'force vector' relevant to the design of the dam?

The force vector is important in the design of the dam because it indicates the direction and magnitude of the force applied by the fluid on the dam. Understanding the force vector helps in ensuring the dam is built to resist these forces effectively.