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: Ball drop question

  1. Oct 8, 2008 #1
    1. The problem statement, all variables and given/known data
    A ball of mass 0.35 kilograms is currently 1.1 meters off the floor and has a speed of 1.3 meters per second straight up. Assuming no energy is converted by air friction, how high will the ball go?

    2. Relevant equations

    3. The attempt at a solution
    Since there is no friction or work, i set the equation as mgh=mgx+1/2mv^2, solving for x(final height) but I get the wrong answer. And I'm pretty sure this is the right equation to use.
  2. jcsd
  3. Oct 8, 2008 #2
    yes I think that's a way to do it, maybe typo on calculator. I got 1.186m
  4. Oct 8, 2008 #3
    1.186? How did u get that? These are the values I plugged in.
    From this x=(((.35*1.1*9.81)-(.(5*.35*1.3^2))/(9.81*.35)
    Using a Ti-83, and not rounding any answers, I get 1.014.

    Im confused...
  5. Oct 8, 2008 #4
    i think easier way is to use kinematics equation : vf^2=vi^2+2ad then add 1.1m with d to get it
  6. Oct 8, 2008 #5
    Yup that did it. Thanks! Though I'm still wondering why my equations didn't work. O well, thanks for help
  7. Oct 8, 2008 #6
    OMG nvm I'm a idiot. I can't do basic algebra -_____-, mine equation does work
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook