- #31
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HAF said:
Does this equation help?
HAF said:
In how many seconds will the n-th wagon pass next to me?
- Thread starter HAF
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Homework Help Overview
The problem involves a train that starts to travel in a straight line at increasing speeds, with the first wagon passing a stationary observer in 4 seconds. The question is to determine how long it will take for the n-th wagon to pass the observer. The context includes concepts of motion, acceleration, and possibly sequences, though the original poster indicates a lack of familiarity with sequences.
Discussion Character
- Exploratory, Assumption checking, Conceptual clarification
Approaches and Questions Raised
- Participants discuss the relationship between time and distance for the wagons, with some suggesting the use of kinematic equations. There are questions about the assumptions regarding acceleration and the interpretation of the problem's wording, particularly concerning the meaning of "increasing speeds" and the initial conditions of the train's position.
Discussion Status
The discussion is ongoing, with various interpretations of the problem being explored. Some participants have provided clarifications about the assumptions regarding constant acceleration and the uniform length of the wagons. However, there is no explicit consensus on a method to derive the time for the n-th wagon, and participants are still questioning how to approach the problem effectively.
Contextual Notes
There are constraints regarding the initial position of the train relative to the observer, which remains unspecified. Additionally, participants note the ambiguity in the phrasing of the problem, particularly regarding whether the time refers to the entire wagon passing or just a point of the wagon.
Does this equation help?
- #32
HAF
- 58
- 6
PeroK said:
What I did this time is this.
vn = vn-1 .atn
which means a=(vn -vn-1) / tn
and that's what I put in equation s=vn-1.tn + 1/2.a.tn2
what I got is this tn = 2s/(vn + vn-1)
Can this somehow help me? I'm really sorry for my stupidness but I can't figure it still out.
- #33
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HAF said:
It's not a good idea to consider intermediate speeds. That is where the complications arise. ##v_0 = 0## for the motion of the train.
- #34
HAF
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And what is your advise?PeroK said:
- #35
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HAF said:
##s = \frac12 at^2##
- #36
HAF
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Nope. I can't figure anything out. I will make a break for a while and then I will try it again because now I can't do it.PeroK said:
Thank You you for everything. I really appreciate it.
- #37
mfb
Mentor
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Plug in L for the first wagon.
Plug in nL for the first n wagons and solve for the new time. You should get ##t \sqrt n##. From there you can take the difference between adjacent wagons.
Plug in nL for the first n wagons and solve for the new time. You should get ##t \sqrt n##. From there you can take the difference between adjacent wagons.
- #38
HAF
- 58
- 6
Plug it where? In s=1/2a.t^2?mfb said:
- #39
HAF
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Thank You guys! I finally got it!mfb said:
- #40
DaveC426913
Gold Member
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Answer:HAF said:
After one second, you are dead.
Sorry. Couldn't resist. Carry on.
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