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: A kid jumps a meter into the air. How long before he lands?

  1. Sep 27, 2010 #1


    User Avatar

    A kid jumps a meter into the air. How long before he lands?

    The answer to this question is .95 seconds.

    I first calculated the time it took for the kid to fall downward. Which was about .45 seconds. But I used the acceleration of 9.8 m/s^2 since he was falling downward. My teachers answer of .95 is assuming that he jumps upward at the rate of 9.8 m/s^2. Is that accurate? I mean, the kid could have jumped up really quickly, but gravity would still pull him down at a rate of .45 sec.

    Thank you for the clarification.

    Also what is this kid's initial velocity? Is it zero?
  2. jcsd
  3. Sep 27, 2010 #2
    they don't really give you a whole lot of stuff to work with, but you do know the acceleration of his jump.

    If you looking for time i might try using energy (if you know how).

    Ef - Ei = 0;

    1/2*mv^2 - mgh = 0;

    you can solve for v and that will be your initial velocity.

    Otherwise I would look into the kinematic equations
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook