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Homework Help: Kinematic formula for projectiles

  1. Sep 11, 2005 #1
    Q: an object is thrown from the ground into the air with a velocity of 20.0m/s at an angle of 27.0 degrees to the horizontal. what is the max height reached by this object?

    i drew the triangle and found vertical side to be 9.08 m/s and horizontal side to be 17.8m/s using sin and cos.
    20 / | 9.08

    but the part i'm having trouble with is how to do the horizontal part of the equation using d=vt. im assuming that i have to use that eqn to find time so i can use that value for the vertical part in finding d, using kinematic formula.
    in the horizontal part d=vt, what would i use as d? i have v as 17.8

    also a side note: for other projectile questions, when would you designate final velocity as unknown, zero, or the negative sign of the initial velocity (ie. initial velocity=14, final velocity = -14) ?
  2. jcsd
  3. Sep 11, 2005 #2
    The key to this problem is to find the time of flight by knowing the initial vertical velocity. From there you'll be able to find time of flight, horizontal distance, vertical distance.
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