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Homework Help: Acceleration Vector Word Problem

  1. Mar 19, 2017 #1
    1. The problem statement, all variables and given/known data
    Famous quarterback Fleet O. Floote is attempting a quarterback draw by running up the middle toward his goal line at 4.6 m/s. A linebacker hits him squarely, and their combined final velocity is 3.8 m/s at an angle of +120.° from the quarterback's original direction. The time it took to change direction at impact was 0.20s. Choose an appropiate horizontal coordinate system and calculate the average acceleration vector of the quarterback during the tackle.

    2. Relevant equations
    a = ΔvΔt

    3. The attempt at a solution
    v1 = 4.6 m/s 90.0°
    v2 = 3.7 m/s 120.°

    v1x = 0 m/s
    v1y = 4.6 m/s

    v2x = 3.7 cos 60° = 1.9 m/s
    v2y = 3.7 sin 60° = 3.2 m/s

    I have this, but I feel that I'm missing something.
  2. jcsd
  3. Mar 19, 2017 #2
    Please draw a diagram, and show it to us. Thank you.

    It seems to me, if the new velocity direction is 120 degrees to the original direction, one of the new components has to be negative.
  4. Mar 19, 2017 #3


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    Hello rf, :welcome:
    Can you post a sketch and compare with what you (were going to) calculate ? Then complete your attempt ?
  5. Mar 19, 2017 #4

    Attached Files:

  6. Mar 19, 2017 #5
    That's only at a 30 degree angle to the QBs original velocity. Did they really mean 120 degrees, or did they really mean 30 degrees?
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