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: Acceleration of water drops problem

  1. Apr 19, 2009 #1
    1. The problem statement, all variables and given/known data

    If the effects of air acting on falling raindrops are ignored, then we can treat raindrops as freely falling objects. Rain clouds are typically a few hundred feet up in the sky. Estimate the speed which raindrops would strike the ground if they were freely falling objects.

    2. Relevant equations

    v0- 0
    s- 200
    a- -9.8

    3. The attempt at a solution
    Ok I know the answer, but I don't understand something. What I did was put all my knowns into the equation. Then this is what it looks like.
    vf^2= -3920
    That is obviously unreal. Then I see that there is a problem with the acceleration. WHY? I thought acceleration of freely falling objects was -9.8.
  2. jcsd
  3. Apr 19, 2009 #2
    Re: What

    Oh and by the way this is not homework. My goal is to make the iPHO in my highschool years. This problem is from University Physics. Which book do you pros recommend to prepare for olympiad problems? University Physics or Fundamental Physics or others?
  4. Apr 19, 2009 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Re: What

    s and a are both negative here.
  5. Apr 19, 2009 #4
    Re: What

    If I'm not mistaken, the acceleration of freely falling objects near the surface of the earth is 9.8 m/s2, so a would be 9.8, try plugging that into the equation. :smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook