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Homework Help: Acceleration When an Object is Slowing

  1. Feb 11, 2016 #1
    1. The problem statement, all variables and given/known data
    If an object is slowing down, does the acceleration automatically have an acceleration of the opposite direction as the initial velocity, even if the question says otherwise?

    Ex. This is a problem from my textbook: A bus is moving at 22m/s[E] for 12s. Then, the bus driver slows doen at 1.2m/s^2 [E] until the bus stops. Determine the total displacement for the bus.

    According to the question, the acceleration of the bus as it slows down is 1.2m/s^2[E]
    2. Relevant equations
    My question doesn't require an equation to answer.

    3. The attempt at a solution
    I looked at the solutions manual, and it uses an acceleration value of 1.2m/s^2[W], an acceleration of the same magnitude, but of opposite direction than the one given in the problem. Does this mean that you always change the direction of acceleration to be the opposite of the given acceleration in the question if an object is slowing down? Do you do the same if it's speeding up?
  2. jcsd
  3. Feb 11, 2016 #2


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    The problem statement was misleading in stating that the acceleration was 1.2 m/s2 [E]. The direction of the acceleration is westward as stated in the solutions.

    All you need to remember is that the direction of the acceleration is opposite to the direction of the velocity when the object is slowing down. They have the same direction when speeding up. This assumes one-dimensional motion.
  4. Feb 11, 2016 #3
    thank you
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