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Physics magnitude and direction?

  1. Sep 3, 2015 #1
    I know this is basic stuff, but if anyone would be willing to help... :)
    At a certain time, a car is 150 meters due west of your house. If it is traveling with a constant velocity of 30m/s 30 degrees south of east, what are the ,magnitude and the direction of its position relative to your house 5 seconds later?

    30m/s(5s)=150m

    150cos30= roughly 130 m
    150sin30=75m

    150m-130m=20m

    mag=sqrt((75^2)+(20^2))=77.6m

    tan inverse(75/20)= 75 degrees

    So, the car is 77.6 meters away from the house at an angle of 75 degrees, south of west.

    Does that seem correct?
    Thanks
     
  2. jcsd
  3. Sep 3, 2015 #2

    TSny

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    Welcome to PF!

    Your answer and method of solution look correct to me.
     
  4. Sep 4, 2015 #3
    Thanks! :)
    Though, should it be inverse tan (20/75)=15 degrees in the last part because the answer in the book was 15° west of south?
     
  5. Sep 4, 2015 #4

    SammyS

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    Yes, tan-1(20/75) ≈ 14.93° .
     
  6. Sep 4, 2015 #5

    TSny

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    75o south of west is the same as 15o west of south. So, either way of expressing the answer is fine.
     
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