24-09-2013, 10:18 PM
The way that I would rationalise when train length is important or not is to consider what circumstances the values that you calculate would be different if you did the same calculation for a very long or very short train.
Clearly, acceleration and speed are going to be independent of train length because otherwise the trian would be stretching or shrinking. If you look at this thread, it has the derivation of the basic formulae for laws of motion which apply to all sizes of object, and hence all lengths of train!
On the other hand, with things to do with distance or time, the length of the train will be important as the whole train has to pass (hence adding train length into the calculation for headway time and headway distance).
Not sure if this approach helps or hinders. Please ask further if it is the latter.
Peter
Clearly, acceleration and speed are going to be independent of train length because otherwise the trian would be stretching or shrinking. If you look at this thread, it has the derivation of the basic formulae for laws of motion which apply to all sizes of object, and hence all lengths of train!
On the other hand, with things to do with distance or time, the length of the train will be important as the whole train has to pass (hence adding train length into the calculation for headway time and headway distance).
Not sure if this approach helps or hinders. Please ask further if it is the latter.
Peter