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Math Help - Physics Question

  1. #1
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    Physics Question

    A car traveling westward at 20 m/s turns around and travels eastward at 15 m/s. If this takes place in 5 s, what is the average acceleration of the car?
    15-20= -5= -1
    5 5

    Is this worked correctly
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  2. #2
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    Re: Physics Question

    No, you have an error with your signs.
    Let's say the eastward direction is the positive direction. Let's demand units of meters and seconds everywhere.

    Then the problem says v_i = -20, v_f = 15 at times t_i = 0, t_f = 5.

    Thus the average acceleration over those 5 seconds is given by:

    a_{ave} = \frac{v_f - v_i}{t_f - t_i} = \frac{(15) - (-20)}{(5) - (0)}= \frac{15 + 20}{5}= \frac{35}{5} = 7.

    Thus the average acceleration over those 5 seconds was 7 meters per second squared.
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