1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

TEST tomorrow in physics and need help on this problem

  1. Sep 11, 2008 #1
    1. The problem statement, all variables and given/known data

    A light-rail train going from one station to the next on a straight section of track accelerates from rest at 1.4 { m/s^2} for 15 { s}. It then proceeds at constant speed for 1100 { m} before slowing down at 2.2 { m/s^2} until it stops at the station.

    What is the distance between the stations?

    How much time does it take the train to go between the stations?

    2. Relevant equations
    (vx)f= (vx)i + ax[tex]\Delta[/tex]t
    xf= xi + (vx)i[tex]\Deltat[/tex] + 1/2ax([tex]\Deltat[/tex])2

    (vx)f2= (vx)i2+2ax[tex]\Deltax[/tex]
    3. The attempt at a solution

    I already know the answer but I cant figure out how to get to the right answer....
    d= 1400m
  2. jcsd
  3. Sep 11, 2008 #2
    Split the question into three different parts. Use equations Vf = Vo + at, x= 1/2(Vf + Vo)t.

    For the first part, you are given Vo, a, t. You need to first find Vf, then x.

    For the second part, you are given x and constant v. You must find t. Think about the units.

    For the third part, you are given a (remember, it's deccelerating so it's - ), Vo, and Vf. Find t, then x.

    At the end, add up all the times from the 3 parts to get 77s. And add the displacements together to get 1400m (I got 1357.5m, but 1400m is correct for the number of sig figs).

    I hoped that helped, and that it wasn't too much information on how to solve the question.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: TEST tomorrow in physics and need help on this problem