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!

2D Kinematics - 2 rocks off a bridge

  1. Feb 5, 2014 #1
    2D Kinematics -- 2 rocks off a bridge

    1. The problem statement, all variables and given/known data

    Heather and Jerry are standing on a bridge 60m above a river. Heather throws a rock straight down with a speed of 14m/s . Jerry, at exactly the same instant of time, throws a rock straight up with the same speed. Ignore air resistance.

    a. How much time elapses between the first splash and the second splash?
    b. Which rock has the faster speed as it hits the water?

    2. Relevant equations



    3. The attempt at a solution

    H and J are 60 m above a river.
    Heather throws the rock down with a speed, v=14 m/s
    Jerry throws it up, v = 14 m/s

    a. I'm assuming that I have to use some vertical/horizontal motion formula, but I don't know...
    b. Don't they both have the same acceleration 9/8 m/s^2 so the same speed?
     
  2. jcsd
  3. Feb 5, 2014 #2
    You will not need to worry about horizontal motion.
    You are right that they will both have the same acceleration, but they both have different initial velocities.

    Look for a kinematics equation that has everything you need. It should have...
    v0, g, t, y0, y

    You have already identified v0, g. What are t, y0, and y?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: 2D Kinematics - 2 rocks off a bridge
  1. 2D Kinematics (Replies: 2)

  2. 2d kinematics (Replies: 7)

Loading...