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: Speed of falling object via derivation/integration

  1. Aug 30, 2010 #1
    1. The problem statement, all variables and given/known data

    A stone is dropped from rest at an initial height h above the surface of the earth. Show that the speed with which it strikes the ground is v=sqrt(2gh)

    2. Relevant equations

    3. The attempt at a solution

    I'm just not sure where to get started. I fully understand how to integrate/derive. I am having trouble understanding what equations to start with.

    EDIT: I assume that I have to derive/integrate somewhere. I understand how to get sqrt(2gh) just by re-arranging the equation vf2 = vi2+2gh
  2. jcsd
  3. Aug 30, 2010 #2


    User Avatar
    Homework Helper

    Assuming no air resistance, then the resultant force acting on the mass m is ma=mg.

    You can write 'a' as 'dv/dt' and integrate.

    Though using kinematics/energy is much simpler.
  4. Aug 30, 2010 #3
    that would give me dv/dt = g. if i integrate with respect to t, id get v=gt

    edit: nevermind, i got it,thanks
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook