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: Easy momentum question

  1. Apr 16, 2009 #1
    1. The problem statement, all variables and given/known data
    A 30.00 kg mass falls from a height of 4.00m. The momentum of the mass just before it hits the ground is?

    2. Relevant equations

    obviously p=mv

    3. The attempt at a solution

    I just can't figure out how to get a velocity for this formula?
  2. jcsd
  3. Apr 16, 2009 #2


    User Avatar
    Homework Helper

    Consider one of these kinematic equations:
  4. Apr 16, 2009 #3


    User Avatar
    Science Advisor
    Gold Member

    There are 2 ways to do this.

    1) Find the velocity using kinematic equations:
    [tex]x = \frac{1}{2}gt^2[/tex]
    you know x and g so you can solve for t. After solving for t you can get the velocity from [tex]v=gt[/tex].

    2) You can also use energy conservation
    and then applying the knowledge of what KE is and momentum is
    to find p directly.
  5. Apr 16, 2009 #4
    yes sir that helped me figure out what the book got, thanks a bunch!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook