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Homework Help: Projectile in motion question

  1. Apr 29, 2007 #1
    A flare was fired straight up at a speed of 25 m/s from the bed of a truck traveling along a level road at a speed of 15 m/s.

    a. Assuming the flare landed back in the bed of the truck, how much time was the flare in the air?

    b. How far horizontally did the flare travel before landing back in the bed of the truck?

    c. What maximum height did the flare reach?

    Some equations that i thought might help with this problem are
    but since i do not no the cange in X or the time i can not use this equation

    To try and figure out this problem i made a chart showing what horizontal and vertical things that i already knew

    H V
    0=ax ay=10 m/s^2
    15 m/s=Vxi Vyi=25 m/s
    =deltaX deltaXy=

    thank you for your time
  2. jcsd
  3. Apr 29, 2007 #2
    One other eqn, Y=Yo+vo(t)+1/2g*t^2 where both Y and Yo are the same in this case, landing in the bed. Remember vo (initial y velocity and acceleration are opposite, just solve for t. The horizontal dispacement is easily computed knowing time and that ax=0. See if you can figure out the third part.

    PS: most of the gravity problems are symmetrical, so time to top is just
    vf=v0+at where vf=0, and the total trip up and down twice that.
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