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: Really though relative motion/momentum question

  1. Oct 12, 2005 #1


    User Avatar

    Okay, really tough for me atleast.
    Answers are 1.15 m/s and 0.346 m/s
    edit: title = tough*
  2. jcsd
  3. Oct 12, 2005 #2


    User Avatar
    Science Advisor

    Conservation of momentum. Or that the center of mass of the girl-plank system must remain stationary since there is no outside force on the system.

    Be careful with speeds. If the plank's speed, relative to the ice is v, then the girl's speed relative to the ice is (1.5+ v) m/s (of course, the plank moves opposite to the girl so v will be negative). The girl's momentum, then, is
    45(1.5+ v) kgm/s and the plank's is 150 v kgm/s. By conservation of momentum, 45(1.5+ v)+ 150v= 0.
  4. Oct 12, 2005 #3


    User Avatar

    Got it... Thanks!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook