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: Kinematics (rectilnear motion) simple

  1. Dec 22, 2013 #1
    Ball 1 is launched with an initial vertical velocity v1=160 ft/sec. Three seconds later, ball 2 is launched with an initial velocity v2. determine v2 if the balls are to collide at an altitude of 300ft.

    not sure where I am going wrong, do I have my limits correct?[URL=http://s1341.photobucket.com/user/nebula-314/media/20131222_191532_zpsf76c1ab5.jpg.html][PLAIN]http://i1341.photobucket.com/albums/o745/nebula-314/20131222_191532_zpsf76c1ab5.jpg[/URL][/PLAIN]
  2. jcsd
  3. Dec 22, 2013 #2
    v2 being initial velocity.
  4. Dec 22, 2013 #3
    I'm not sure what you're doing here, but if I were you I would use the following equation to calculate t for the first ball to reach 300ft, then using that t minus 3 (because the 2nd ball was launch 3 seconds later) and the same equation I would calculate v2.

    [itex]\Delta[/itex]x= [itex]\frac{1}{2}[/itex]a[itex]t^{2}[/itex]+[itex]v_{0}[/itex]t

    Just remember that here we take upside direction to be positive, hence a=-g and if you are measuring distance in ft you should use g=32.17 ft/s^2 , or convert ft to meter and use g=9.8 m/s^2

    Let me know how it goes :)
    Last edited: Dec 22, 2013
  5. Dec 23, 2013 #4
    Oh i was trying to derive that equation, and perhaps save some steps.
  6. Dec 23, 2013 #5
    But your solution did help a lot thanks.
  7. Dec 23, 2013 #6
    oh I see! I guess sometimes it's just easier to stick to the basics! :tongue2:

    No problem at all, happy to help
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted