Mass of weight to keep gate closed

[jc911]

Hi All,

Cannot seem to figure out the question below. I`ve attached an image of the question.

I basically need to find the mass of the weight W.

The hinged gate will open when the water height is 12ft.

The gate is a 5ft wide L shaped gate, hinged at point A.

I`ve gone down the line of CW = CCW moments but cannot seem to answer this.

Any help greatly appreciated. I really want to understand the entire process behind the calculation so I can work through these problems myself going forward :)

This is first year fluid dynamics.

Thanks,
James

 

[jvicens]

Hi James,

Thank you for sharing your question and providing an image of the problem. It seems like you are on the right track by using the principle of moments to solve for the mass of the weight W. Here are the steps that you can follow to solve this problem:

1. Draw a free body diagram of the gate and the weight W. This will help you visualize the forces acting on the system.

2. Write down the equations of equilibrium for the horizontal and vertical forces. This will help you determine the unknown forces acting on the system.

3. Use the principle of moments to solve for the unknown force acting on the weight W. This can be done by taking moments about point A, the hinge point of the gate.

4. Once you have determined the unknown force, you can use Newton's second law (F=ma) to solve for the mass of the weight W.

Remember to always include units in your calculations and to double check your work. I hope this helps and good luck with your fluid dynamics studies!