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 ball is thrown

  1. Sep 23, 2007 #1
    A ball is thrown horizontally from the top of a building and lands a distance d from the foot of the building after having been in the air for a time T and encountering no significant air resistance.

    If the building were twice as tall, the ball would have

    a) landed a distance 2d from the foot of the building
    b) been in the air a time 2T
    c) been in the air a time T squareroot2
    d) reached the ground with twice the speed it did from the shorter building


    x=x0 + v0xt + 1/2at^2
    vx = v0xt +axt
    and vx^2 = V0x^2 +2a (xf - xi)

    Are, I think, the right equations. I don't know what to do though :(
     
  2. jcsd
  3. Sep 24, 2007 #2
    D'oh, it was C. Thanks anyways :)
     
  4. Sep 24, 2007 #3

    CompuChip

    User Avatar
    Science Advisor
    Homework Helper

    Note that the other three are equivalent: if the ball is in the air for a time 2T and the horizontal velocity does not change (no resistance) it will land at a distance 2d and since the velocity is v = a T it would also go twice as fast. So if any of these were true, then the other three would be true as well. Only b and c are clearly contradictory, so you just had to decide which one of them was true :smile:
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook