1. Not finding help here? Sign up for a free 30min 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!

Low Level Physics Problem 1D Motion

  1. Sep 14, 2004 #1

    A rock is dropped from a sea cliff and the sound of it striking the ocean is heard 3.4s later. If the speed of sound is 340 m/s, how high is the cliff?

    Could somebody map this one out for me, it isn't making any sense.
  2. jcsd
  3. Sep 15, 2004 #2
    Solve the equations.

    Attached Files:

  4. Sep 15, 2004 #3


    User Avatar
    Staff Emeritus
    Science Advisor

    First, do you know a formula for distance an object falls in t seconds?
    Solve that for t1 (the time until the rock hits the water) as a function of d (the height of the cliff).

    Second, you are given that the speed of sound is 340 m/s so you can calculate the time, t2 neccessary for the sound to come back up a distance d.

    Since t1+ t2= 3.4 seconds, you can add those two formulas, involving d, to get an equation. Solve the equation for d.
  5. Sep 15, 2004 #4
    Umm....Another question. Where in the world are you standing to hear the splash?
  6. Sep 17, 2004 #5
    Since the acceleration of the rock is uniform i.e under the affect of gravity, couldn't you use the equations of motion?

    u=0, a = 9.81, t = 3.4


    I know that's not the information he was given but would it work? The only assumption I've made is that the rock was dropped from rest.
  7. Sep 17, 2004 #6
    The time given in this question is not the time the rock takes to reach the ocean but is the total time the rock reaches the ocean plus the time for the splash sound to travel back to the dropper. So i don't think it would work here.
  8. Sep 18, 2004 #7
    Ah yes, you are right. I didn't think :blushing: :smile:
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Low Level Physics Problem 1D Motion