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: Can someone help me with a physics problem with momentum?

  1. Jun 26, 2008 #1
    1. The problem statement, all variables and given/known data
    A .150kg baseball is dropped from rest. IF the magnitude of the baseball's momentum is .780 kg m/s just before it lands on the ground, from what height was it dropped?

    2. Relevant equations


    3. The attempt at a solution

    I found the final velocity and know that the inital position is zero and the initial velocity is zero obviously. i tried to go back to the kinematic equations to solve for final position but i do not know time and i do not know acceleration.
  2. jcsd
  3. Jun 26, 2008 #2
    Use an energy balance and choose you title with care please....
  4. Jun 26, 2008 #3
    energy balance?
  5. Jun 26, 2008 #4


    User Avatar
    Homework Helper

    Hi alyson42,

    You don't know the time, but are you sure you don't know the acceleration?
  6. Jun 26, 2008 #5
    acceleration due to gravity? just 9.81 m/s? can it be that easy?
  7. Jun 26, 2008 #6


    User Avatar
    Homework Helper

    Sounds good; your acceleration units aren't quite right, but maybe that's just a typo. Depending on how you set up the problem you might need to be careful with signs, but it seems to be a straightforward problem.
  8. Jun 26, 2008 #7
    i got the correct answer. You are a genius. Thanks for the help!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook