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!

Homework Help: Relative Velocity

  1. Jun 16, 2010 #1
    I want to calculate the instantaneous relative velocity between two objects. Object A is at location (x1,y2) moving towards the origin (0,0) at velocity V. How do you calculate object A's relative velocity to object B at location (x2,y2)?
  2. jcsd
  3. Jun 16, 2010 #2


    User Avatar
    Science Advisor

    You need to specify velocity of B relative to the origin. If the speeds are not near the speed of light, it is simply a vector subtraction of B velocity from A velocity.

    If the difference is near the speed of light, you need to take into account special relativity effect - check Google.
  4. Jun 16, 2010 #3
    B is a stationary observer. I am trying to calculate how fast object A is approaching B, even though object A is moving towards the origin.

    I haven't been in a physics class since college, but remember that it probably has something to do with the law of cosines. I don't think it is just a simple vector subtraction.

    I appreciate any help. Thank you.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook