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Homework Help: Projectile motion of mortar round problem

  1. Jul 4, 2011 #1
    1. The problem statement, all variables and given/known data

    A mortar round is fired over a building that is 2600m away, at an initial velocity of 240m/s. The building is 1600m tall and 100m wide. Calculate the distances which are safe from mortar shells left of the building.

    2. Relevant equations

    1.) Vy(t) = Vyo - at

    2.) Sy(t) = Syo + Vyo - 0.5at^2

    3. The attempt at a solution

    I can use the above equations to find an angle by guessing a distance where the projectile lands to then calculate the max height of the arc and see if it could clear the building but it seems like this would be doing it the wrong way around as I would have to keep making guesses.

    Is there some way I could factor in the height of the building to my equations?
  2. jcsd
  3. Jul 4, 2011 #2


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    The phrase "left of the bulding" is seriously not helpful. If (x,y) = (0,0) is the origin, located at the mortar, where "up" is +y and "to the right" is +x, then, assuming the building is centered at 2600m to the right of the mortar, any trajectory that falls short of the point (2550,0) and exceeds the point (2650,1600) will be safe, from the building's point of view.
  4. Jul 5, 2011 #3
    Sorry that was meant to be right of the building, where the building is to the right of the mortar origin.
  5. Jul 5, 2011 #4
    I cant edit the post but the mortar is at the origin and the building is 2600m on the positive x axis from the origin.

    I'm still pretty stumped with this. I could make guesses at the angle or the distance it lands but I dont know how I could be more precise?
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