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Homework Help: Vector Drawing Help

  1. Oct 22, 2013 #1
    1. The problem statement, all variables and given/known data

    A puppy runs 4km west, 2km south, and then 5km 30 degrees south of east. Determine the total distance he walked and his net displacement. If it took him 1.2 hours to complete the run, find his average speed and his average velocity.

    a) Draw all vectors with correct direction and magnitudes. State the scale you are using to represent the vectors.
    b) Use head to tail vector addition to find the resultant displacement. Show your addition of vectors graphically. (Use different colors for each of the vectors as well as the resultant).
    c) State the displacement and distance traveled by puppy.
    d) Calculate the average speed and average velocity of the puppy. Show all calculations including equation and substitution with units.

    2. Relevant equations

    Pythagorean Theorm: a^2+b^2=c^2

    velocity = distance/time

    3. The attempt at a solution

    For part A I draw the vectors and it created a triangle with the lengths of 4km, 2km, and 5km.

    The distance traveled by puppy I determined to be 11km adding all the distances the puppy ran. As for the displacement I am unsure of, I think it is 0 because it started off running 4km west then 2km south and then back to the original by running 5km.

    For average velocity I did velocity = distance divided by time which gave me 11Kmh/1.2h = 9.1666666667
  2. jcsd
  3. Oct 22, 2013 #2
    It's hard to help if we can't see your diagram. For example, he definitely didn't travel in a triangle. Please reconsider your diagram. Also, average velocity is not distance divided by time. It is vector displacement divided by time. To get the vector displacement, you need to get the diagram right.
  4. Oct 23, 2013 #3


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    What Chester said. Sounds like you drew a vector roughly "north of east" rather than the stated "south of east". Have another go.
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