Resultant displacement with multiple segments

  1. I have to displacment problems that i cant get right.

    While John is traveling along a straight interstate highway, he notices that the mile marker reads 233. John travels until he reaches the 155-mile marker and then retraces his path to the 172-mile marker. What is John's resultant displacement from the 233-mile marker?
    I thought the answer for this one would be 61 but it is marked wrong.

    Bob walks 57 m and then he walks 125 m. What is Bob's displacement if he walks east then west?
    I thought the answer for this one would be 68 but it is marked wrong.
  2. jcsd
  3. For the second problem, Try negative -68, cause he goes past the origin, to the negative side. Also, the first answer may be negative also, not sure though.
  4. Thanks, that was it. for some reason I was thinking displacement couldnt be negative.
  5. displacement is a vector quantity. all vector quantities are affected by direction. therefore all vector quantities should be labeled with a direction (wether it be shown with a positive/negative sign, bearing on a compass,etc)
  6. Both answers would have been correct had you included the negative sign for both. :smile:
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