# Variable mass/force oscillations

1. Feb 1, 2012

### 123physics123

Hi,
I'm working on a problem that i would like your input on. I have a solution but i would like to see how others would approach it since my solution is more of a hypothesis until we continue with the testing phase.
In the most basic form, this project can be described as a hanging container on a spring. It can be described as a 1-D spring mass problem. The container is filled with a material that is a solid that has been crushed into smaller bits. At time t=0 the material starts to empty out of the container via the opening located on the side of the container near the bottom. Due to the enormous size of the container the material near the bottom is subject to high pressure that acts to compact the material. Also the interior surfaces of the container are not smooth but have rings that are equally spaced that act to separate the material into sections. The rings do not stick out enough to support a significant amount of the material above them but do act to interrupt the flow. Putting all of this together the flow of the material is neither continuous nor made up of discrete blocks. It is somewhere in between.
I know i have been pretty vague but i would appreciate if you could tell me how you would approach this.
My current solution is to consider the mass of the system to be just the container, with the mass of the material represented by a periodic applied force due to the material hitting the bottom of the container in semi discrete blocks. This results in an applied impact force that is periodic and decreases at a constant rate each time it is applied. Another alternative is to consider the system as having a decreasing mass but this would not take into account the non continuous flow and the periodic impacts on the bottom of the container.

Some background: I am an engineering student working on a project with an industry client. My group has completed a preliminary solution that we will be testing this term but i would like to have alternative approaches, should the testing provide results that do not match our hypothesis. I'm not looking for worked out solutions or anything specific, just general approaches. Even better would be if anyone has any references or experiments i could refer to that are similar in nature. Thanks

2. Feb 1, 2012

### Studiot

You might get more replies if you stated what you wanted to achieve/work out as well as describing the system.

That is what is the actual question?

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