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Homework Help: Train turning, tangential acceleration and total acceleration

  1. Sep 17, 2010 #1
    1. (a)A train slows down at a constant rate as it
    rounds a sharp circular horizontal turn. Its
    initial speed is not known. It takes 16.6 s to
    slow down from 86 km/h to 30 km/h. The
    radius of the curve is 162 m.
    As the train goes around the turn, what is
    the magnitude of the tangential component of
    the acceleration?
    Answer in units of m/s2.

    (b) As the train goes around the turn, what is
    the sign of the tangential component of the
    acceleration? Take the direction in which the
    train is moving to be the positive direction.
    1. +
    2. Not enough information
    3. 0
    4. −

    (c)At the moment the train’s speed is 50 km/h,
    what is the magnitude of the total accelera-
    tion?
    Answer in units of m/s2.




    2. Relevant equations
    atangential = d|v|/dt
    not sure on others


    3. The attempt at a solution
    I tried part (a) with atangential = d|v|/dt
    where atangential = |30-86|/16.6=3.37349 km/h^2
    then converting to m/s^s by times 3600s and dividing 1000m and getting 12.1446 m/s^2
    wrong
     
  2. jcsd
  3. Sep 17, 2010 #2

    PhanthomJay

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    You are messing up your units and conversions....first change km/hr to m/s, find the change in v, then divide by t (in seconds) to get the tangential acceleration.
     
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