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Homework Help: Projectile Motion Help?

  1. Mar 31, 2010 #1
    A ball is fired out of a cannon and flies a total distance of 235 meters. The ball has a total flight time of 47s. What is the maximum height and the vertical and horizontal components?

    1. The problem statement, all variables and given/known data

    df= 235m
    t= 47s

    2. Relevant equations


    3. The attempt at a solution

    v=5 (i dont know where to plug this number into. I could answer this problem if it gave me the trajectory angle, but it is unknown?)
  2. jcsd
  3. Mar 31, 2010 #2

    ok so u basically have the horizontal component here. if u put subscripts, it is dx = vx*ttot
    therefor vx = 5m/s

    ok next, you know at in projectile motion, at max height velocity = 0m/s right?
    so vf = vi + at. t = 1/2 the total time because tup = tdown for projectile motion of the same height. remember this is all in the y component, so a would = 9.8m/s^2. plug and solve for vi ( which is also vy ) and u have ur y component.

    next for maximum height you have found you vy component so what do u do? find another formula! what do we know again?? v at max height = 0m/s right? and you have vi sooooo which formula includes vf <--- v at max and vi AND DISTANCE IN THE Y DIRECTION??? you already know. plug and chug and u shuld have it.
  4. Mar 31, 2010 #3
    ok, so the horizontal component is 5. I didn't know where the 5 went.

    and just checking my answers, did your vertical component equal .02

    and also my max height was 460.62m.

    thanks. :)
  5. Mar 31, 2010 #4
    now looking at it, .02 doesn't look right?
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