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: Question on Velocity, two cars moving away from each other

  1. Aug 9, 2010 #1
    i would greatly appreciate any help towards this......i thought my workings were correct, but i don't think they are now...
    http://i21.photobucket.com/albums/b283/NMchugh/Various/velocity.png Question


    vAx = 80 vAy = 0 vBx = 50 cos(60 vBy = 50 sin(60

    First we look at the horizontal X- component
    vBAx = vBx - vAx
    vBAx = (50 cos60) - (+80)
    vBAx = 25 - 80 = -55km/h

    Next we look at the vertical y- component
    vBAy = vBy - vAy
    vBAy = (50 sin60) - (0)
    vBAy = 43.3km/h

    vBA = √(vBAx)² + (vBAy)² = √(-55)² + (43.3)² = 70
     
  2. jcsd
  3. Aug 9, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Looks OK to me except that you have motion in the negative x direction as positive. For example, I'd say that vAx = - 80 km/h, not +80. That will end up affecting your direction for the velocity.
     
  4. Aug 9, 2010 #3
    Looks like you did it right.
     
  5. Aug 9, 2010 #4
    my friend seems to think this is a check i can do to see if my answer is correct (gives the correct angle)
    does this answer mean my workings are wrong?

    tan∅ = vABy = 43.3 = 0.41, ∅ = tanˉ¹ ( 0.41) =22.4
    vABx 105
     
  6. Aug 10, 2010 #5
    i have the same question aswell but a is 95 KM and b 125 KM,got the the angle point and gt stuck there thought my answer is wrong,so i don't know what to do.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook