- #1
Rothiemurchus
- 203
- 1
Why does the surface of some lakes become concave just before the water falls over a weir?
Why do some lakes have a concave surface before water falls over a weir?
In summary, the surface of some lakes becomes concave just before the water falls over a weir due to adhesion and surface tension. The deeper water molecules fall over first, followed by the top layers, as the surface tries to maintain its original configuration. This phenomenon can be observed in experiments measuring surface tension. Additionally, dropping detergent on the surface can temporarily cause the concave shape to disappear.
- #2
marlon
- 3,792
- 11
Rothiemurchus said:
Two words : adhesion and surface tension...
The deeper watermolecules will fall over first, then the top layers of the water. the reason for this is that the surface will always try to maintain or restore the original configuration once some perturbation has occured...
Think of what would happen if you would slowly move a ring out of water. the surface-layers will try to stick to the rings...they want the ring to stay in the water and thus maintain the original configuration. These things are used in experiments to measure the surface tension of fluids in general...
marlon
- #3
Rothiemurchus
- 203
- 1
If I dropped some detergent on the surface the concave shape would disappear briefly?
1. How does water falling over a weir create energy?
Water falling over a weir creates energy through the process of potential energy being converted into kinetic energy. As the water flows over the weir, it gains speed and momentum which can then be harnessed by turbines to generate electricity.
2. What is the purpose of a weir in a water system?
A weir is used in a water system to control the flow of water and regulate the water level. It can also be used to divert water to different areas and prevent flooding.
3. How does the design of a weir affect the flow of water?
The design of a weir, including its height, shape, and angle, can impact the flow of water by creating different levels of turbulence and resistance. A well-designed weir can efficiently control the flow and prevent excessive erosion.
4. What are the environmental impacts of a weir?
The construction of a weir can have both positive and negative environmental impacts. On one hand, it can regulate water levels and provide a source of clean energy. On the other hand, it can disrupt the natural flow of a river and affect the habitats of aquatic animals.
5. How is the flow rate of water over a weir measured?
The flow rate of water over a weir is typically measured using a formula called the Francis formula, which takes into account the height of the weir, the width of the opening, and the speed of the water. Other methods include using ultrasonic meters or venturi meters.
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