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Impact of trolley - hand calculation method!

  1. Jul 9, 2014 #1
    Hello,

    Been a while since I posted on here, nice to be back :) .

    I just want some pointers as to the methodology for an impact load case that I'm looking at. I've attached a very basic sketch of a trolley which is travelling at a known velocity and impacts a rigid structure at it's base.

    What I'm going to do is to determine the stiffness of the trolley at it's impact location, then calculate the deflection and resulting force by utilising conservation of energy between the KE of the trolley and the spring energy of the system. So I can do all that and obtain the impact force and look at my stresses. But once the trolley impacts, it will decelerate rapidly and tend to rotate about the pivot shown on the bottom view of the attached diagram. The restoring moment due to weight of the trolley relative to the CoG will not be enough to prevent it from rotating clockwise toward the rigid structure.

    I'm confused on how to work out how far the trolley will rotate and whether it will impact the rigid structure at the top - denoted by "point A" on the attached bottom image.

    I was going to use the inertia of the trolley to determine this, but I'm very confused, because I have both linear kinetic energy and rotational kinetic energy. If I can work out the height that the CoG will rise to on impact then I can calculate the angle of rotation, but is this too simplistic? I'd have to equate the ImageUploadedByPhysics Forums1404928873.146751.jpg rotational KE to the PE, but PE=mgh is linear :/ ?

    I'm really confused! Any pointers for my approach would be so appreciated.

    Many thanks
     
  2. jcsd
  3. Jul 11, 2014 #2
    I wasn't able to glean what you're trying to calculate. Could you give me the units (e.g. newtons, meters, kg, etc...) of what you're trying to calculate.

    Hints
    1) draw the force vectors in figure 2. And then draw the vector you want to calculate.

    2) don't use the word utilize or any of its weird spelling. You know what they say about people you "utilize"? They make a tool out of you and ize.
     
  4. Jul 11, 2014 #3
    Hey, thanks for your reply.

    I don't need units, it's a the method I'm discussing! I a freelance chartered engineer and stress analyst - a d u use the word utilise often; it's a word lol.

    I have solved the problem now, but wanted to discuss my approach! Maybe there is a better way of doing it!
     
  5. Jul 11, 2014 #4
    Apologies for typos - can't type on my iPhone :/
     
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