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: Length contraction of two spaceships

  1. Apr 27, 2013 #1
    1. The problem statement, all variables and given/known data
    Two space ships, each a hundred metres long when measured at rest, travel toward each other with a speed of 0.85c relative to the Earth.

    2. Relevant equations
    λ = 1 / √1 - (v2/c2)
    x' = λ(x - vt)
    L' = L / λ

    3. The attempt at a solution
    Well to be honest i may be missing an equation or something but that's what i was given.

    I find that the relative velocity of one spaceship to another (according to newton) would be 1.5c. This doesn't work using the equations above. I know i have to find the relative velocity according to Einstein's theory but i don't know how.
  2. jcsd
  3. Apr 27, 2013 #2
    So, you are trying to find the relative velocity of one to the other?

    Let the first space ship be space ship A and the second be space ship B.

    Consider ##v_{BA}=\frac{v_B-v_A}{1-\frac{v_Av_B}{c^2}}##.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted