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: Momentum. resulting velocity. Rocket

  1. Mar 9, 2008 #1
    [SOLVED] Momentum. resulting velocity. Rocket

    1. The problem statement, all variables and given/known data

    On earth, an astronaut and equipment weigh 1,960.0 N. While weightless in space, the astronaut fires a 100 N rocket backpack for 2.0 s. What is the resulting velocity of the astronaut and equipment?

    I have to be missing something. I tried using every formula given to me in class and I cannot get anywhere. Please help. Thanks.

    2. Relevant equations

    p=mv
    Ft= (mf)(vf)-(mi)(vi)
    Ft=ma+v(difference of m/t)
    m1v1=m2v2

    3. The attempt at a solution
    I tried a few and can't get a relevant answer. I really do not know where to begin with the rocket.
     
    Last edited: Mar 9, 2008
  2. jcsd
  3. Mar 9, 2008 #2

    G01

    User Avatar
    Homework Helper
    Gold Member

    Don't worry about the rocket itself. You only care about what it does. It applies a constant force over a specified time? How does this affect the astronaut in terms of momentum?
     
  4. Mar 9, 2008 #3
    difference of momentum= (100N)(2.0s) = 200kgm/s

    200kgm/s= (1960N/ 9.8m/s^2) V

    V=1m/s

    I first found the difference of momentum which is force * time. then used the equation momentum=mass*velocity. Is this correct?
     
  5. Mar 10, 2008 #4

    G01

    User Avatar
    Homework Helper
    Gold Member

    Looks Good!:smile:
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook