Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Vector Problem

  1. Oct 23, 2007 #1
    I need help on this vector problem. We haven't started yet, but this was one of the problems on the syllabus.

    Your home is 15.0 km at a direction 40 degrees northwest. If you walked 10.0 km north, in what direction and distance would you have to walk to get home?

    Your help will be greatly appreciated
  2. jcsd
  3. Oct 23, 2007 #2
    Welcome to Physicsforums! hope you enjoy your stay.

    A vector is a quantity that has a magnitude(like 15 km) and direction (like north or south or an angle such as 40deg).

    A good place is always to start with a diagram so you can visually see what is going on.

    Your home is 15 km away but 40 degrees north OF west. Can you draw this?

    I am not permitted to help you unless you show an effort or ask probing questions.
  4. Oct 26, 2007 #3
    so far, i've done this and i'm not sure whether or not im correct.

    l \
    l \
    l \ --->15 km
    l \
    l___\ ----> 40 degrees

    sorry, im really bad at making diagrams on the computer. It just wanst coming out right. Basically i mae a triangle, with a hypotenuse of 15 and one of the angles (the one opposite the hypotenuse) is 40 degrees.
    Last edited: Oct 26, 2007
  5. Oct 26, 2007 #4
    Looks correct to me. However, it is not teh angle opposite to the hypotenuse. it is the angle with the x axis and hypotenuse.

    Now you walk north 10km. What direction and distance do you walk to reach home?
  6. Oct 26, 2007 #5
    Is the answer 11.1?

    I used pythagorean theorem.


    10^2 + b^2= 15^2

    He needs to walk 11.1 km east to get home

    Please let me know whether this is right or wrong.
  7. Oct 26, 2007 #6
    yea it is right. Try to keep more decimal places. 11.1 is quite different than 11.18.
  8. Oct 26, 2007 #7
    Ok, thanks alot. You've been a great help.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook