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Calculating the magnitude of displacement

  1. Aug 5, 2012 #1
    A car us driven at a velocity of 72km/h EAST for 0.50hr, 48km/h NORTH for 0.25hr, and 62km/h WEST for 0.50hr. Calculate the magnitude of its displacement.

    Attempt at the solution:

    Distance = Speed * Time

    (72 x 0.5) + (48 x 0.25) - (62 x 0.5) = 17km

    However, the answer in the book says 13km and I can't figure out how..
  2. jcsd
  3. Aug 5, 2012 #2
    If you go 1 km north and 1 km east, you're not 2 km away from where you started; you're about 1.4 km away. This is the quantity you're being asked for. What do you know about the pythagorean theorem?
  4. Aug 5, 2012 #3
    Oh okay, I get it.. So i have to get the difference of the East and West vectors and use pythagorean theorem to find the resultant vector.