I carried out a small scale practical experiment to check the computer model. I used a 900x150 pin kerb balanced on a stack of concrete paving blocks 400mm high. When it hit the ground (not a hole) it continued to rotate by only about 50mm from the stone blocks. That's nowhere near what my model had predicted. I went back to the model and found the problem: When a block is pivoting about its end, the moment of inertia is 4 times larger than when it rotates about its middle. I had accounted for this, but had forgotten about the principle "conservation of momentum". What I should have done is to also divide the angular speed by 4 to maintain the same angular momentum. When I made this correction, the model now behaves very similarly to the pin kerb. However, this upsets all the figures I gave in my previous message. So please ignore them.
I've got a fairly busy day today so I'll have to wait until tonight to do any more, but "I'll be back".
Reply | with quote | Posted by Steve Gray 27th August 2003ce 13:09 |
Stone Shifting 2 (nigelswift, Aug 26, 2003, 17:00)- Re: Stone Shifting 2 (Jane, Aug 26, 2003, 17:16)
- Re: Stone Shifting 2 (Steve Gray, Aug 26, 2003, 17:46)
- Re: Stone Shifting 2 (GordonP, Aug 26, 2003, 20:44)
- Re: Stone Shifting 2 (FourWinds, Aug 27, 2003, 11:24)
- Re: Stone Shifting 2 (nigelswift, Aug 29, 2003, 09:10)
- Steve's idea to fix a pivot log under the stone (nigelswift, Aug 30, 2003, 08:24)
- Which Method? (nigelswift, Aug 31, 2003, 07:09)
- Pi in the sky (baza, Aug 31, 2003, 17:44)
- Re: Stone Shifting 2 (jimit, Sep 01, 2003, 19:39)
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