Help Laws of Motion and question help

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Homework Help Overview

The discussion revolves around a problem involving the laws of motion, specifically focusing on a train's acceleration, uniform motion, and deceleration. The original poster describes a scenario where a train accelerates, travels at a constant speed, and then decelerates, seeking to calculate the total distance between two stations.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss finding acceleration using the distance and time provided. There is uncertainty about which time to use and how to apply the relevant equations. Questions arise about the initial conditions and the implications of starting from rest.

Discussion Status

Participants are actively engaging with the problem, with some offering guidance on using the equations of motion. There is a focus on clarifying the steps needed to find acceleration and the subsequent distance calculations. Multiple interpretations of the problem are being explored, particularly regarding the application of the equations.

Contextual Notes

There is an emphasis on understanding the relationships between distance, time, and acceleration, with participants questioning assumptions about initial velocity and the application of the equations. The original poster expresses difficulty in proceeding with the calculations.

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Homework Statement


A train moves off from a station and accelerates uniformly for 30.0 s over a distance of 225 m. It continues with the speed acquired for another 135 s, then the driver applies the brakes and the train comes to rest with uniform retardation at the next station in a further 10.0 s. Calculate the distance between the two stations


Homework Equations



s= ut + 1/2at^2


The Attempt at a Solution


i am still stuck please someone help me go through the steps
 
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Can you find the acceleration over the 225m distance given you have time?
 
Last edited:
No I don't understand which time to use
 
well the question states that the train travels 225m in 30s - try using these.
 
So I divide those 2 then times it by 135 to get the acceleration?
 
use the equation you stated, s= ut + 1/2at^2
 
But I don't know how to get acceleration would u be 0 because it started from rest and is the time 30 if I put in equation?
 
that is correct.
 
Yes but how do you get acceleration?
 
  • #10
as i said before use this equation... s= ut + 1/2at^2
you know what s, u, and t are can you not solve the equation for a?
 
  • #11
a = 2(s - ut)/t^2 would I rearrange to this??
 
  • #12
Yes that is correct however you know that u=0 right? because as you said earlier the train starts from rest, and u represents the initial velocity of the train.
 
  • #13
Yes I know that so after I've calculated the acceleration what do I do next?
 
  • #14
Well what you're trying to do is find the total distance to the second train station... so you're told the train travels at this acceleration you've found for another 135s, you need to find the change in distance with this acceleration.
 

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