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Homework Help: Average Acceleration Question

  1. Mar 11, 2014 #1


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    1. The problem statement, all variables and given/known data
    A motorboat traveling in a straight line has a velocity of +4.0 m/s at some point in time. After 5.0 seconds, its velocity is +7.0 m/s. What is its average acceleration during this time?

    2. Relevant equations

    avg accel.=change in velocity/change in time

    3. The attempt at a solution

    7.0 m/s-4.0 m/s=3.0 m/s

    [itex]\frac{3 m/s}{5s}[/itex]

    0.60 m/s^2.

    I dont understand why is it m/s^2 versus m/s. What does the plus sign indicate in the question in front of 7.0 and 3.0?
  2. jcsd
  3. Mar 11, 2014 #2
    Well, ##\frac{m}{s^{2}}## is just the unit of acceleration. When you have ##\frac{m}{s}##, then divide that by a time, then the denominator becomes ##s^{2}##. And the plus sign is just used to indicate the direction of the velocity, and to indicate that the boat travels in a straight line.
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