Freshman Kinematics Question: The Jumper Upstairs

Fun question:

You live in the dorms and your upstairs neighbor, LeBrian Skinner, is a serious basketball player.  He is about to declare for the NBA draft, but he fears that his merely average height will put him at a disadvantage.  To compensate for his relative shortness, LeBrian decides that he needs to have a vertical jump of at least 36 inches.

In the evening you can hear LeBrian practicing his vertical leap, since he lives directly above you: you hear a loud creak when he first jumps followed by a loud thump when he lands again.  You use a stopwatch to time the interval between the moment he first leaves the floor and the moment when he lands again.  You measure this interval as 0.8 seconds.

Assuming that LeBrian lands with his legs fully extended (in the same position as when he leaves the floor), how high is he jumping?  Is it enough?

Give it some thought, and then find the answer here.



  1. Danny L says:

    Thanks, you just gave me an excuse to do an integral on the back of a liquor store receipt. Been a while since I've done one long-hand.