1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I'm having trouble trying to solve this particular problem.

  1. Jan 28, 2010 #1
    1. The problem statement, all variables and given/known data

    A car makes a trip due north for three-fourths of the time and due south one-fourth of the time. The average northward velocity has a magnitude of 13 m/s, and the average southward velocity has a magnitude of 11 m/s. What is the average velocity (magnitude and direction) for the entire trip?

    2. Relevant equations
    not sure

    3. The attempt at a solution

  2. jcsd
  3. Jan 28, 2010 #2
    If I walk forward 2 miles in half an hour, and then walk backwards 1 mile in half an hour, how far have I walked forward and how long did it take me?
  4. Jan 28, 2010 #3
    1 mile and 1 hour
  5. Jan 28, 2010 #4
    1 mile and 1 hour
  6. Jan 28, 2010 #5
    So your average velocity is one miler per hour in the forward direction, right? Use that same logic for your problem. Your average speed is close to 12 m/s (actually 12.5, since you were going 13 m/s for a longer time than you were going 11 m/s), but your average velocity has a direction associated with it. You were going 12.5 m/s on average, but you weren't going that fast north.
  7. Jan 28, 2010 #6
    okay I understand its northward, but the part I don't get is what formula to use?
  8. Jan 28, 2010 #7
    You basically just need to do the same simple algebra we did in my example. The only difference is that I gave you distances and time instead of velocity. It's a lot easier than you think. Try a few samples using different values of time and see what you get.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook