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

1. Sep 27, 2010

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. Sep 27, 2010

### fizzynoob

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