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: Free Fall help

  1. Sep 15, 2010 #1
    1. The problem statement, all variables and given/known data

    An alert hiker sees a boulder fall from the top of a distant cliff and notes that it takes 1.3s for the boulder to fall the last 3rd of the way to the ground. Ignore air resistance.a) what is the height of the cliff in meters? b) If in part a) you get 2 solutions what does the extraneous one represent?

    2. Relevant equations

    3. The attempt at a solution

    looking at the last 3rd
    Vi = ?
    Vf = 0 m/s
    a = -9.8 m/s/s
    t = 1.3s
    x = ?

    possibly going to use this equation: x = xo +vit +.5at^2 ?
  2. jcsd
  3. Sep 15, 2010 #2
    you should use the equation y = yo +vit +.5gt^2 for vertical motion.
    also Vi should equal zero, as the boulder begins from rest in the y-axis and Vf should equal the final velocity as the boulder hits the ground
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook